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American Automobile Association (AAA)

Motor club and leisure travel organization serving North America

Web Link:


The Alliance of Automobile Manufacturers (AAM) is a trade association that represents car manufacturers, including:

Web Link:


The American Automobile Manufacturers Association (AAMA) is a trade association that represented car manufacturers headquartered in the United States.
After the purchase of Chrysler by German Daimler-Benz the organization has been dissolved on December 31, 1998.

absolute viscosity

The ratio of shear stress to shear rate.
It is a fluid's internal resistance to flow.

The common unit of absolute viscosity is the poise (see viscosity).

Absolute  viscosity  divided  by the fluid's density equals kinematic viscosity.

absorber oil

Oil used to selectively absorb heavier hydrocarbon components from a gas mixture.
Also called wash oil or scrubber oil.


Process by, which one substance draws into itself another substance;
the assimilation of one material into another;

in petroleum refining, the use of an absorptive liquid to selectively remove components from a process stream.

Examples: a sponge picking up water; an oil recovering gasoline from wet natural gas.


Association des Constructeurs Europeens Automobiles
(Association of the European Automobile Manufacturers)
is the new association of the European automobile manufacturers, formed in February 1991.
ACEA is engaged in a broad range of activities including safety and environmental concerns and any regulations which have a direct impact on the European automobile industry.
ACEA members are all the European motor vehicle manufacturers including Ford Europe, GM Europe, Scania, and Volvo. At present, only PSA Peugeot Citroen is not a member of ACEA but cooperates with ACEA in the field of lubricating oils and fuels.



A member of an important and fundamental category of chemical substances characterized by having an available reactive hydrogen and requiring an alkali to neutralize them. Acid solutions usually have a sour, biting, and tart taste, like vinegar. pH is less than 7.

acid sludge

The residue left after treating petroleum oil with sulfuric acid for the removal of impurities. It is a black, viscous substance containing the spent acid and impurities.

acid treating

A refining process in which unfinished petroleum products, such as gasoline, kerosene, and lubricating oil stocks, are contacted with sulfuric acid to improve their color, odor, and other properties.


The amount of free acid in any substance.


An agent or chemical substance added to a product and used for imparting new, or for improving existing characteristics of lubricating oils or greases.

Common petroleum product additives are:

additive level

The total percentage of all additives in an oil.
(Expressed in % of mass [weight] or % of volume)


The force or forces causing two materials such as a lubricating grease and a metal, to stick together.


Adhesion of the molecules of gases, liquids, or dissolved substances to a solid surface, resulting in relatively high concentration of the molecules at the place of contact; e.g., the plating out of an anti-wear-additive on metal surfaces.

Also, any refining process in which a gas or a liquid is contacted with a solid, causing some compounds of the gas or liquid to adhere to the solid; e.g., contacting of lube oils with activated clay to improve color.

See clay filtration


A highly dispersed suspension (Colloidal System) of fine solid or liquid particles in a gas.

Petroleum solvents are commonly used either as carriers or as vapor pressure depressants in packaged aerosol specialty products. Petroleum products are also applied in aerosol form in agricultural oil applications and oil mist lubrication.


Alternate Fuel Vehicle


American Gear Manufacturers Association

Web Link:


Alliance of International Auto Manufacturers (AIAM)

The organization no longer exists

Similar activities are now undertaken by:


Web Link:

air entrainment

The incorporation of air in the form of bubbles as a dispersed phase in the bulk liquid. Air may be entrained in a liquid through mechanical means and/or by release of dissolved air due to a sudden change in environment. The presence of entrained air is usually readily apparent from the appearance of the liquid (i.e., bubbly, opaque, etc.) while dissolved air can only be determined by analysts.

aliphatic hydrocarbon

hydrocarbon in which the carbon atoms are joined in open chains, rather than rings.

See normal paraffin.


In chemistry, any substance having basic properties. The term is applied to hydroxides of ammonium, lithium, potassium, and sodium. They are soluble in water; have the power to neutralize acids and form salts. They turn red litmus blue. In a more general sense, the term is also applied to the hydroxides of the so-called alkaline earth metals: barium, calcium, and strontium.


Any of a series of monovalent radicals having the general formula CnH2n+1, derived from aliphatic hydrocarbons by the removal of a hydrogen atom; for example, CH3- (methyl radical, from methane).


product of an alkylation process.

alkylated aromatic

benzene-derived synthetic lubricant base with good hydrolytic stability (resistance to chemical reaction with water) and good compatibility with mineral oils.

Used in turbines, compressors, jet engines, and hydraulic power steering.


In refining, the chemical reaction of a low-molecular-weight olefin with an isoparaffin to form a liquid product, alkylate, that has a high octane number and is used to improve the antiknock properties of gasoline. The reaction takes place in the presence of a strong acid catalyst, and at controlled temperature and pressure. Alkylation less commonly describes certain other reactions, such as that of an olefin with an aromatic hydrocarbon.

Almen EP lubricant tester

A Journal bearing machine used for determining the load-carrying capacity or Extreme Pressure properties (EP) of gear lubricants.

ambient temperature

Temperature of the area or atmosphere around a process, (not the operating temperature of the process itself).


Free of water, especially of crystallization.

aniline point

The minimum temperature for complete miscibility of equal volumes of aniline and the sample under test ASTM Method D 611. A product of high aniline point will be low in aromatics and naphthenes and, therefore, high in paraffins. Aniline point is often specified for spray oils, cleaning solvents, and thinners, where effectiveness depends upon aromatic content.

In conjunction with API gravity, the aniline point may be used to calculate the net heat of combustion for aviation fuels.

anti-foam agent

An additive used to control foam.

Two types of additives are used to reduce foaming in petroleum products:

See foaming

antifreeze solution

A fluid, such as ethylene or propylene glycol, which is added to or used to replace the water in the cooling system of engines in order to prevent freezing.

anti-friction bearing(s)

A type of bearing using rollers, cones or balls.
They are also known as rolling element bearings.

anti-icing additive

Aubstance added to gasoline to prevent ice formation on the throttle plate of a carburetor.
Anti-icing additives are of two types:

  1. Those that lower the freezing point of water
  2. Those that alter the growth of ice crystals so that they remain small enough to be carried away in the air stream.


Resistance to detonation or pinging in spark-ignition engines.

Resistance of a gasoline to detonation in a combustion chamber.

See antiknock indexoctane number.

antiknock compounds

Substances which raise the antiknock quality of a gasoline, as expressed by octane number.
Historically, tetraethyl lead (lead alkyl) has been the most common antiknock compound, but its use is being phased out under Environmental Protection Agency (EPA) regulations.
Coming into increasing use as octane boosters are toluene and oxygenated organic type substances such as methyl tertiary butyl ether (MTBE) and tertiary amyl methyl ether (TAME).

antiknock index

The average of the Research Octane Number and Motor Octane Number;
a measure of the octane quality of a gasoline.

According to EPA and FTC regulations the antiknock index of any gasoline sold in the USA must be displayed on any pump dispensing the gasoline for use in motor vehicles.

See octane number.


Chemical additive which is added to lubricating oils to increase their resistance to oxidation.

anti-seize compound

Grease-like substance containing graphite, moly or metallic solids (Copper, Zinc, Silver or Lead), which is applied to threaded joints, particularly those subjected to high temperatures, to facilitate easy separation when required.

anti-wear additive

additive in a lubricant that reduces friction and excessive wear.

See boundary lubrication.


The American Petroleum Institute (API) is a trade association that promotes U.S. petroleum interests, encourages development of petroleum technology, cooperates with the government in matters of national concern, and provides information on the petroleum industry to the government and the public.

Web Link:

API Engine Service Classification System

Classifications and designations for lubricating oils for automotive engines developed by API in conjunction with SAE and ASTM.
An recently also with ILSAC.

API Gear Lubricant Service Designation

Classifications and designations for lubricating oils for automotive transmissions developed by API in conjunction with SAE and ASTM.

API gravity

A nonscientific and arbitrary scale expressing the gravity or density of liquid petroleum products.
The measuring scale is calibrated in terms of degrees API.
It may be calculated in terms of the following formula:

API Gravity Degrees Formula

apparent viscosity

The ratio of shear stress to rate of shear of a non-Newtonian fluid such as lubricating grease, or a multi-grade oil, calculated from Poiseuille's equation and measured in poises. The apparent viscosity changes with changing rates of shear and temperature and must, therefore, be reported as the value at a given shear rate and temperature (ASTM Method D 1092).


Derived from, or characterized by, the presence of the benzene ring.

unsaturated hydrocarbon identified by one or more benzene rings or by chemical behavior similar to benzene.
The benzene ring is characterized by three double bonds alternating with single bonds between carbon atoms (compare with olefins).
Because of these multiple bonds, aromatics are usually more reactive and have higher solvency than paraffins and naphthenes.
Aromatics readily undergo electrophylic substitution; that is, they react to add other active molecular groups, such as nitrates, sulfonates, etc.

Aromatics are used extensively as petrochemical building blocks in the manufacture of pharmaceuticals, dyes, plastics, and many other chemicals.


Association of South-East Asian Nations

Web Link:

ash content

The percent by weight of residue left after combustion of an oil or fuel sample.
(ASTM Method D 482 or D 874 [sulfated ash]).

Lubricating oil detergent additives contain metallic derivatives, such as barium, calcium, and magnesium sulfonates, that are common sources of ash.
Ash deposits can impair engine efficiency and power.

See detergent


American Society of Lubrication Engineers.

This society is still in existence but is now known as the Society of Tribologists and Lubrication Engineers (STLE).
The ASLE had published standards for machine tool lubricants.


Microscopic projections on metal surfaces resulting from normal surface-finishing processes. Interference between opposing asperities in sliding or rolling applications is a source of friction, and can lead to metal welding and scoring.
Ideally, the lubricating film between two moving surfaces should be thicker than the combined height of the opposing asperities.

See boundary lubrication, EP additive


Black to dark-brown solid or semisolid cemetitious material which gradually liquefies when heated and in which the predominating constituents are bitumen's.
These occur in the solid or semisolid form in nature; are obtained by refining petroleum; or are combinations with one another or with petroleum or derivatives thereof.


Essentially composed of, or similar to, asphalt; frequently used to describe lubricating oils derived from crude oils which contain asphalt.


The American Society for Testing and Materials (ASTM) is a professional society that is responsible for the publication of test methods and the development of test evaluation techniques.

Web Link:


Technical Committee of the Petroleum Additive Manufacturers

ATF - Automatic Transmission Fluid

Fluid for automatic transmissions in motor vehicles.
Automatic transmission fluids must have a suitable coefficient of friction, good low-temperature viscosity, and anti-wear properties.
Other necessary properties are:

See corrosion, foaming.


Association Technique de L'Industrie Europeene des Lubrifiants.

(European Oil Marketers Association)

Web Link:


  1. In realtion to Fuels & Combustion in Internal Combustion Engines it is the spontaneous ignition, and the resulting very rapid reaction, of a portion or all of the fuel-air mixture in an engine.
    The flame speed is many times greater than that which follows normal spark ignition. The noise associated with it is called knock

  2. In realtion to Lubricants it is the Temperature at which the lubricant will self ignite when exposed to air and continue to burn.



Additive included in the formulations of water-mixed cutting fluids or coolants,
to inhibit the growth of bacteria promoted by the presence of water,
thus preventing the unpleasant odors that can result from bacterial action.


Standard unit of liquid measurement in the petroleum industry.

Used to measure quantities of crude oil, gasoline and fuel oils.

Equivalent of 42 U.S. Gallons.


Any of a broad class of chemical compounds, including alkalis, that react with acids to form salts, plus water.
Also known as hydroxides. Hydroxides ionize in solution to form hydroxyl ions (OH-); the higher the concentration of these ions, the stronger the base. Bases are used extensively in petroleum refining in caustic washing of process streams to remove acidic impurities, and are components in certain additives that neutralize weak acids formed during oxidation.

Base Oil

A base oil is a base stock or blend of base stocks used in an API-licensed engine oil.

Base oil interchangeability

Refers to an API approved system, that reduces testing costs by permitting the interchangeable use of certain base oils, without requiring a full engine test program for each of the base oils.

Base Stock

A base stock is a mineral hydrocarbon or synthetic lubricant component that is produced by a single manufacturer (independent of crude source or manufacturing location), that meets the same manufacturer's specification, and that is identified by a unique formula, product identification number, or both.


Any quantity of material handled or considered as a "unit" in processing.
I.e., any sample taken from the same "batch" will have the same properties and/or qualities.


basic machine component designed to reduce friction between moving parts and to support moving loads.

There are two main types of bearings:

  1. rolling contact bearings (also called anti-friction bearings) commonly ball or roller
  2. sliding (plain) bearings, either plain journal (a metal jacket fully or partially enclosing a rotating inner shaft) or pad-type bearings, for linear motion.

Rolling-contact bearings are more effective in reducing friction. With few exceptions, bearings require lubrication to reduce wear and extend bearing life.

Bench Test

A laboratory test that measures various specific performance parameters of an engine oil.
Specialized test equipment is used for bench testing.


The mineral montmorillonite, a magnesium-aluminum silicate.
Used as a treating agent, also, as a component of drilling mud, and in greases.


Colorless liquid hydrocarbon, C6H6, with one ring of carbon atoms. Made from coal tar and by catalytic reforming of naphthenes, it is used in the manufacture of phenol, styrene, nylon, detergents, aniline, phthalic anhydride, biphenyl, nitrobenzene, chlorbenzene; as a solvent; and as a component of high-octane gasoline.

benzene insoluble

That portion of the normal pentane insoluble in used lubricating oils which is not soluble in benzene, and which may include the insoluble contaminants from external sources, some matter produced by oxidation and thermal decomposition of the oil, the oil additives, or the fuel.

(It is tested by ASTM Method D 893).


The process of mixing lubricants or components for the purpose of obtaining the desired physical and/or chemical properties (see compounding).


Fluorescence; the color of an oil by reflected light which could differ from its color by transmitted light.


In an internal combustion engine, seepage of fuel and gases past the piston rings and cylinder wall into the crankcase, resulting in crankcase oil dilution and deposit formation.

See positive crankcase ventilation.

boiling point

The temperature at which a substance boils, or is converted into vapor by bubbles forming within the liquid; it varies with pressure.


The liquid which collects in the bottom of a vessel (tower bottoms, tank bottoms), either during a fractionating process or while in storage.

boundary lubrication

The state of lubrication when conditions exist that do not permit the formation of a lubricant film capable of completely separating the moving parts.
As a result the asperities of the moving parts come in contact and a high wear rate results.

Brookfield viscosity

apparent viscosity of an oil, as determined under test method ASTM D 2983.
Since the apparent viscosity of a non-Newtonian fluid holds only for the shear rate (as well as temperature) at which it is determined, the Brookfield viscometer provides a known rate of shear by means of a spindle of specified configuration that rotates at a known constant speed in the fluid.
The torque imposed by fluid friction can be converted to absolute viscosity units (centipoises) by a multiplication factor. See viscosity, shear stress. The viscosities of certain petroleum waxes and wax-polymer blends in the molten state can also be determined by the Brookfield test method ASTM D 2669.

bright stock

Refined, high viscosity base oils usually made from residual stocks by suitable treatment, such as a combination of solvent extraction, propane asphating or catalytic dewaxing.

British Thermal Unit (BTU)

The quantity of heat required to raise, by 1°F, the temperature of one pound of water at its maximum density (39.2°F).


The material which collects at the bottom of storage tanks, usually composed of oil, water and foreign matter.
Also called Bottoms or Bottom and Wettling or Watter.


British Technical Council


A gas that is composed of either or both of two isomeric, flammable, gaseous hydrocarbons, C4H10, of the paraffin series: n-butane or isobutane.

Also called, along with propane, liquefied petroleum gas (LPG).



Corporate Average Fuel Economy

Minimum Fuel Economy for Cars and Light Trucks established by U.S. Congress.

Administered jointly by EPA and NHTSA.

It has been 27.5 MPG for Cars and 20.7 MPG for Light Trucks for many years, but in 2012 verious new regulations were approved so that future CAFE has to be improved annualy, and the current goal is to reach CAFE of 54.5 MPG by 2020


  1. The amount of heat required to raise the temperature of 1 gram of water 1°C, at or near the temperature of maximum density. This unit is called a "small calorie", or "gram calorie".
  2. The amount of heat required to raise the temperature of 1 kg of water 1°C.
    This unit is called a "large calorie" or "kilogram-calorie".

capillary viscometer

A viscometer in which the oil flows through a capillary tube.


California Air Resources Board

carbon monoxide (CO)

A colorless, odorless, poisonous gas, formed by the incomplete combustion of any carbonaceous material (e.g., gasoline, wood, coal). CO is the most widely distributed and most commonly occurring air pollutant, with motor vehicles being the primary source of man-made emissions, although emission controls are reducing the automobile's contribution. It is estimated that more than 90% of atmospheric CO comes from natural sources, such as decaying organic matter.

See catalytic converter


Device used with an internal combustion engine to atomize and mix fuel with air in the proper proportion for efficient combustion at all engine speeds. It controls the engine's power output by throttling, or metering, the air-fuel mixture admitted to the cylinders.

The automobile carburetor is a complex mechanism designed to compensate for many variables over a wide range of speeds and loads.

Intake air is drawn through the venturi, a constricted throat in the air passage that causes a pressure reduction in the air stream, which draws fuel from the carburetor bowl through either the main jet or the idle jet.

The fuel is atomized by the high-velocity air, and the resulting air-fuel mixture is piped through the intake manifold to the individual cylinders, where it is burned.

A throttle plate between the venturi and the cylinders controls power and speed by controlling the volume of air-fuel mixture reaching the cylinders. In most carburetors, closing of this (venturi) throttle valve shuts down the main jet and activates the idle jet, which provides the fuel-rich mixture that idling requires. An accelerator pump in the carburetor provides momentary fuel enrichment when the accelerator pedal is depressed rapidly, to compensate for the sudden influx of air.

During cold starting, a choke (or butterfly valve) restricts airflow to the carburetor, thus enriching the mixture for faster starting. The choke on most automotive engine carburetors is operated automatically by a thermostatic spring, which opens the choke as the engine warms up.

See fuel injection

Carrier Oil

Oil (Petroleum), usually solvent neutral (SN) or process oil, used to "carry" or dissolve and/or disperse additives, which would otherwise be too viscous or even solid, and therefore not easily mixed with the Base Stock Oil.


Substance that causes or speeds up a chemical reaction without itself undergoing an associated change; catalysts are important in a number of refining processes.

catalytic converter

An emissions control device, incorporated into an automobile's exhaust system, containing catalysts - such as platinum, palladium, or rhodium - that reduce the levels of hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx) emitted to the air. In the catalytic converter, HC and CO are oxidized to form carbon dioxide (CO2), and NOx are reduced to nitrogen and oxygen.
Three-way catalytic converters that control all three substances require associated electronic controls for precise regulation of oxygen levels in the exhaust gas. Catalytic converters are also effective in removing PNA (polynuclear aromatic) hydrocarbons. Cars equipped with catalytic converters require unleaded gasoline, since the lead in tetraethyl lead, an antiknock compound, is a catalyst "poison."

See hydrocarbon emissions

catalytic cracking

In refining, the breaking down at elevated temperatures of large, high-boiling hydrocarbon molecules into smaller molecules in the presence of a catalyst.
The principal application of catalytic cracking is the production of high-octane gasoline, to supplement the gasoline produced by distillation and other processes.
Catalytic cracking also produces heating oil components and hydrocarbon feedstocks, such as propylene and butylene, for polymerization, alkylation and petrochemical operations.


formation of an air or vapor pocket (or bubble) due to lowering of pressure in a liquid, often as a result of a solid body, such as a propeller or piston, moving through the liquid; also, the pitting or wearing away of a solid surface as a result of the collapse of a vapor bubble. Cavitation can occur in a hydraulic system as a result of low fluid levels that draw air into the system, producing tiny bubbles that expand explosively at the pump outlet, causing metal erosion and eventual pump destruction. Cavitation can also result when reduced pressure in lubricating grease dispensing systems forms a void, or cavity, which impedes suction and prevents the flow of greases.


Comite des Constructeurs d' Automobile du Marche Commun
(European Common Market Automobile Manufacturers Association)
European vehicles. This organization was dissolved at the end of 1990.
ACEA, the new association of the European automobile manufacturers, formed in February 1991, has decided to retain the CCMC oil sequences and their original designation for a transitional period.


Coordinating European Council


The chief substance composing the cell walls or fibers of all plant tissue, a polymeric carbohydrate with the general formula (C6H10O5)x: it is used in the manufacture of paper, textiles, filters, etc.

centistoke (cSt)

The worldwide unit of kinematic viscosity.


  1. The phenomenon observed among gear lubricants and greases when they thicken due to cold weather or other causes, to such an extent that a groove is formed through which the part to be lubricated moves without actually coming in full contact with the lubricant.

  2. A term used in percolation filtration; may be defined as: a preponderance of flow through certain portions of the clay bed.


Commercial Item Description used in many cases in lieu of military specification (MIL).

clay filtration

refining process using fuller's earth (activated clay) or bauxite to adsorb minute solids from lubricating oil, as well as remove traces of water, acids, and polar compounds.

See adsorption

cloud point

The temperature at which paraffin wax or other solid substances begin to crystallize or separate from the solution, imparting a cloudy appearance to the oil when chilled (ASTM Method D 97).


Chemical Manufacturers Association is the trade association responsible for the development and administration of the Petroleum Additives Panel Product Approval Code of Practice (CMA Code).


(a) The undesirable accumulation of carbon (coke) deposits in the internal combustion engine or in a refinery plant.

(b) The process of distilling a petroleum product to dryness.


  1. a solid, liquid, or gaseous substance made up of very small, insoluble, nondiffusible particles (as single large molecules or masses of smaller molecules) that remain in suspension in a surrounding solid, liquid, or gaseous medium of different matter

  2. a state of matter consisting of such a substance dispersed in a surrounding medium All living matter contains colloidal material, and a colloid has only a negligible effect on the freezing point, boiling point, or vapor pressure of the surrounding medium

[Greek kolla, glue + -oid; coined by T. Graham (1805-69), Scottish chemist]

Colloidal particles are 5 to 5000 angstroms in size. In a gas or liquid medium, they do not settle and are not easily filtered.

Colloids are usually ionically stabilized by some form of surface charge on the particles to reduce the tendency to agglomerate.

A lubricating grease is a colloidal system, in which metallic soaps or other thickening agents are dispersed in, and give structure to, the liquid lubricant.

SynLube™ Lube−4−Life™ Lubricants are colloidal systems, in which solid graphite, moly and PTFE colloids are dispersed in synthetic liquid lubricants.


A factor in the identification, rather than in the quality rating of a petroleum products and lubricants, except where staining or appearance are considerations.


Rapid oxidation of a fuel (burning).

The products of an ideal combustion process are water (H2O) and carbon dioxide (CO2); if combustion is incomplete, some carbon is not fully oxidized, yielding carbon monoxide (CO).

A stoichiometric combustible mixture contains the exact quantities of air (oxygen) and fuel required for complete combustion. For gasoline, this air-fuel ratio is about 15:1 by weight or about 9,500:1 by volume.

If the fuel concentration is too rich or too lean relative to the oxygen in the mixture, combustion cannot take place.

See internal combustion engine.

combustion chamber

In an internal combustion engine, the volume, bounded by the top of the piston and the inner surface of the cylinder head, in which the air-fuel charge ignites and burns. Valves and spark plugs are fitted into the combustion chamber.

complex grease

A lubricating grease thickened by a complex soap consisting of a normal soap and a complexing agent.


The addition of fatty oils and similar materials to lubricants to impart special properties. Lubricating oils to which such materials have been added are known as compounded oils.

compounded oil

Mixture of a petroleum oil with animal or vegetable fat or oil. Compounded oils have a strong affinity for metal surfaces; they are particularly suitable for wet-steam conditions and for applications where lubricity and extra load-carrying ability are needed.
They are not generally recommended where long-term oxidation stability is required.

copper strip corrosion

The gradual eating away of copper surfaces as the result of oxidation or other chemical action.
It is caused by acids or other corrosive agents.


The gradual eating away of metallic surfaces as the result of oxidation or other chemical action.
It is caused by acids or other corrosive agents or by electro-chemical reaction of the metal with its environment.

Corrosion Inhibitor

Substance which protects a metal against corrosion by substances which originate from products of combustion, or from deterioration of the lubricant.


Petroleum refining process in which large-molecule liquid hydrocarbons are converted to small-molecule, lower-boiling liquids or gases; the liquids leave the reaction vessel as unfinished gasoline, kerosene, and gas oils. At the same time, certain unstable, more reactive molecules combine into larger molecules to form tar or coke . The cracking reaction may be carried out under heat and pressure alone (thermal cracking), or in the presence of a catalyst (catalytic cracking).

Crankcase oil

Lubricant used in the crankcase of the internal combustion engine.

crude oil

Complex, naturally occurring fluid mixture of petroleum hydrocarbons, yellow to black in color, and also containing small amounts of oxygen, nitrogen and sulfur derivatives and other impurities. Crude oil was formed by the action of bacteria, heat, and pressure on ancient plant and animal remains, and is usually found in layers of porous rock such as limestone or sandstone capped by an impervious layer of shale or clay that traps the oil (reservoir). Crude oil varies in appearance and hydrocarbon composition depending on the locality where it occurs, some crudes being predominantly naphthenic, some paraffinic, and others asphaltic. Crude is refined to yield petroleum products.

See asphalt, distillation, sour crude, sweet crude, naphthene, paraffin.


Commissione Tecnica de Unificazione nel l'Autoveicolo



Ability of an oil to separate from water, as determined by test method ASTM D 1401 or D 2711. Demulsibility is an important consideration in lubricant maintenance in many circulating lubrication systems.


additive that promotes oil-water separation in lubricants that are exposed to water or steam.

See demulsibility.


The mass of a unit of volume of a substance as compared to Water which has a density of one.


Diesel Engine Oil


The ability of an oil to keep working surfaces of equipment clean (i.e. free from contaminants) by holding oil-insoluble material in suspension thus preventing deposition where it would be harmful.


Important additive component of engine oils and some industrial lubricants, such as paper machine oils and hydraulic fluids; helps control deposits by preventing contaminants of combustion from directly contacting metal surfaces and, in some cases, by neutralizing acids. A detergent is usually a metallic (commonly barium, calcium, or magnesium) compound, such as a sulfonate, phosphonate, thiophosphonate, phenate, or salicylate. Because of its metallic composition, a detergent leaves a slight ash when the oil is burned. A detergent is normally used in conjunction with a dispersant.

detergent oil

Is a lubricating oil possessing special sludge-dispersing properties usually conferred on the oil by the incorporation of special additives. Detergent oils hold formed sludge particles in suspension and thus promote cleanliness especially in internal-combustion engines. However detergent oils do not contain "detergents" such as those used for cleaning of laundry or dishes. Also detergent oils do not clean already "dirty" engines, but rather keep in suspension the sludge that petroleum oil forms so that the engine remains cleaner for longer period. The formed sludge particles are either filtered out by Oil Filters or drained out when oil is changed.


Diesel Heavy Duty  Engine Oil

dielectric strength

A measure of the of insulating properties of electrical insulating oils for use in electrical cables, transformers, circuit breakers, and similar apparatus (Tested by ASTM Method D 877).

diester oil

A synthetic Iubricating fluid made from esters: also called ester oil or an organic ester, formed by reacting a dicarboxylic acid and an alcohol; properties include a high viscosity index (V.I.) and low volatility. With the addition of specific additives, it may be used as a lubricant in compressors, hydraulic systems, and internal combustion engines.


Deutsche Industrie Norm
(German Industrial Standards).


Highly reactive straight-chain hydrocarbon with two double bonds between adjacent carbon atoms.

See olefin


A dispersing agent, which holds a very finely divided substance in a dispersed state in the carrier fluid. Such as sludge or a wear particles in a motor oil.

In engine oil dispersant is additive that helps prevent sludge, varnish, and other engine deposits by keeping particles suspended in a colloidal state (see colloid) within the bulk oil.

Dispersants are normally used in conjunction with detergents.

A dispersant can be distinguished from a detergent in that the former may be non-metallic and thus does not leave an ash when the oil is burned; hence the term ashless dispersant.


Wide range of and any product produced by distillation.


The process of condensing into liquid the vapours distilled from any liquid such as water, petroleum or alcohol.

In the petroleum oil industry it is the primary refining step, in which crude oil is separated into fractions, or components, in a distillation tower, or pipe still. Heat, usually applied at the bottom of the tower, causes the oil vapors to rise through progressively cooler levels of the tower, where they condense onto plates and are drawn off in order of their respective condensation temperatures, or boiling points - the lighter-weight, lower-boiling-point fractions, exiting higher in the tower. The primary fractions, from low to high boiling point, are: hydrocarbon gases (e.g., ethane, propane); naphtha (e.g., gasoline); kerosene, diesel fuel (heating oil); and heavy gas oil for cracking. Heavy materials remaining at the bottom are called the bottoms, or residuum, and include such components as heavy fuel oil (fuel oil) and asphaltic substances (see asphalt). Those fractions taken in liquid form from any level other than the very top or bottom are called sidestream products; a product, such as propane, removed in vapor form from the top of the distillation tower is called overhead product. Distillation may take place in two stages: first, the lighter fractions - gases, naphtha, and kerosene - are recovered at essentially atmospheric pressure; next, the remaining crude is distilled at reduced pressure in a vacuum tower, causing the heavy lube fractions to distill at much lower temperatures than possible at atmospheric pressure, thus permitting more lube oil to be distilled without the molecular cracking that can occur at excessively high temperatures.

See hydrocracking.


Deutsche Koordinierungs ausschuss

(German Coordinating Council)

dropping point

In general, the dropping point is the temperature at which the grease passes from a semisolid to a liquid state. This change in state is typical of greases containing conventional soap thickeners. Greases containing thickeners other than conventional soaps may, without change in state, separate Oil

dry lubricant

Solid material left between two moving surfaces to prevent metal-to-metal contact, thus reducing friction and wear. Such materials are especially useful in the region of boundary lubrication, and for lubrication under special conditions of extremely high or low temperature where usual lubricants are inadequate. They may be applied in the form of a paste or solid stick, or by spraying, dipping, or brushing in an air-drying carrier which evaporates leaving a dry film. Or can be present in a "sol", a colloidal suspension in Water, Alcohol or Oil.

Some examples of dry lubricants are:



Energy Conserving (1.5% Fuel Conserving) and Energy Conserving Level II (2.7% Fuel Conserving). It is the ability of lubricant to conserve fuel in gasoline automotive type engines when compared to ASTM HR-2 SAE 20W-30 reference motor oil.

elastohydrodynamic lubrication

Lubrication model modified to take into consideration the elastic properties of the bearing material and the viscosity increase of the lubricant under concentrated load.

emissions (automotive)

The three major pollutant emissions for which gasoline-powered vehicles are controlled are: unburned hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). Diesel-powered vehicles primarily emit NOx and particulates.
Motor vehicles contribute only a small percentage of total man-made emissions of other atmospheric pollutants, such as sulfur oxides.
Evaporative HC emissions from the fuel tank and carburetor are adsorbed by activated carbon contained in a canister installed on the vehicle.
Blow-by HC emissions from the crankcase are controlled by positive crankcase ventilation (PCV). Exhaust emissions of HC, CO, and NOx - the products of incomplete combustion - are controlled primarily by a catalytic converter, in conjunction with exhaust gas recirculation (EGR) and increasingly sophisticated technology for improving combustion efficiency, including electronic emission controls and Fuel Injection.


The ability of a non-water soluble fluid (such as oil) to form an emulsion with water.


A substance used to promote or aid the emulsification of two liquids and to enhance the stability of the emulsion.

additive that promotes the formation of a stable mixture, or emulsion, of oil and water.

Common emulsifiers are: metallic soaps, certain animal and vegetable oils, and various polar compounds (having molecules that are water-soluble at one extremity of their structures and oil-soluble at the other).


A mechanical mixture of two insoluble liquids such as oil and water.

Energy Conserving Oil

Engine oil categories developed by SAE, ASTM, and API, based on an oil's fuel-saving performance in passenger cars, vans, and light trucks.

Originally "Energy Conserving" rating was based on the average fuel economy gain of a five vehicle test, this however proved to be too costly and difficult to repeat the test results.

Later engine-stand test was used for "Energy Conserving" oil which must have produced a fuel economy improvement of 1.5% or greater over a reference oil (ASTM HR-2) in a standard ASTM test procedure. An "Energy Conserving II" oil must have produced a fuel economy improvement of at least 2.7%.

With ILSAC GF-2 and API SJ the "Energy Conserving II" rating was dropped and only one "Energy Conserving" rating was used, but with different values based on motor oils SAE Viscosity rating.

(Note: the fuel economy gain of SynLube™ Lube−4−Life® SAE 5W-50 Motor Oil in ASTM test is 5% when compared to HR-2 test oil)

Since all current motor oil ratings starting with API SK, ILSAC GF-3 incorporate "Energy Conserving" performance into their specifications, and therefore most motor oils on the market today are "Energy Conserving". The rating is not as important as it once was.

In actual vehicle operation, the fuel economy obtained by these lubricants differs, depending on vehicle type, operating conditions, and driving habits. Therefore the fuel saving ability of any Motor Oil is mostly a theoretical value.

In real life day-to-day operation, a fuel saving of less than 2% is not possible to verify, since tank-to-tank fuel economy in normal driving can vary by up to 20%.

See fuel-economy oil.

engine deposits

Hard or persistent accumulations of sludge, varnish, and carbonaceous residues due to blow-by of unburned and partially burned (partially oxidized) fuel, and/or from partial breakdown of the crankcase lubricant. Water from condensation of combustion products, carbon, residues from fuel or lubricating oil additives, dust, and metal particles also contribute. Engine deposits can impair engine performance and damage engine components by causing valve and ring sticking, clogging of the oil screen and oil passages, and excessive wear of pistons and cylinders. Engine deposits are increased by short trips in cold weather, high-temperature operation, heavy loads (such as pulling a trailer), and over-extended oil drain intervals.

Engine Oil

An engine oil is a lubricating agent that can be classified according to one or a combination of the viscosity grades identified in Table 1 of the most recent edition of SAE Standard J300. Engine OiIs are also called Motor Oils. Engine oils include diesel engine oils (DEO and passenger car motor oils (PCMO).

Engine test

Also called engine sequence test or sequence test, it refers to a test of an oil's performance using a full-scale engine operating under laboratory conditions.

Engler degree

A measure of viscosity. The ratio of the time of flow of 200 ml of the liquid tested, through the viscometer devised by Engler, to the time required for the flow of the same volume of water gives the number of degrees Engler.


Engine Oil Licensing and Certification System (EOLCS) refers to an administrative process and legally enforceable system by which API authorizes marketers of engine oil to display an API Mark or Marks on oils that meet specified industry standards, as prescribed in a formal licensing agreement.


Environmental Protection Agency

Agency of the federal executive branch, established in 1970 to abate and control pollution through monitoring, regulation, and enforcement, and to coordinate and support environmental research.

EP additive

Lubricant additive that prevents sliding metal surfaces from seizing under conditions of extreme pressure (EP). At the high local temperatures associated with metal-to-metal contact, an EP additive combines chemically with the metal to form a surface film that prevents the welding of opposing asperities, and the consequent scoring that is destructive to sliding surfaces under high loads. Reactive compounds of sulfur, chlorine, or phosphorus are used to form these inorganic films.

EP agent

An Extreme Pressure additive introduced into a lubricant to improve the load-carrying or anti-weld qualities.

EP lubricant

Any of the lubricating oils or greases which contain an Extreme Pressure additive specifically introduced to prevent metal-to-metal contact in the operation of highly loaded gears. In some cases, this is accomplished by the additive reacting with the metal to form a protective film.


Esters are chemical compounds consisting of a carbonyl adjacent to an ether linkage.
They are derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol.
Esters are usually derived from an inorganic acid or organic acid in which at least one -OH (hydroxyl) group is replaced by an -O-alkyl (alkoxy) group, and most commonly from carboxylic acids and alcohols.
That is, esters are formed by condensing an acid with an alcohol.

Many chemically different "esters" due to their usually excellent lubricity are used for various reasons as either "additives" or "base stocks" for lubricants.

exhaust gas recirculation (EGR)

System designed to reduce automotive exhaust emissions of nitrogen oxides (NOx).
The system routes exhaust gases into the carburetor or intake manifold; the gases dilute the air-fuel mixture (see combustion) which lowers peak combustion temperatures, thus reducing the tendency for NOx to form.



An animal or vegetable oil which will combine with an alkali to saponify and form a soap.

fiber grease

A grease with a distinctly fibrous structure, which is noticeable when portions of the grease are pulled apart.

filler (lubricants)

Any substance, such as talc, mica, or various powders, which may be added to a grease to make it heavier in weight or consistency, but which serves no useful function in making the grease a better lubricant.
(Note: Starch filler may also be added to certain lubricating oil or other lubricants).

film strength

The property of an oil which enables it to maintain an unbroken film on lubrIcated surfaces under operatIng conditions, where other otherwise there would be scuffing or scoring of the surfaces.

Fire Point

The lowest temperature at which an oil or other product vaporizes sufficiently rapidly to form above its surface an air-vapor mixture which when subjected to a source of ignition or a flame, will ignite and continue to burn.

Typically for most Petroleum products the Fire Point is about 50°F above the Flash Point.

Flash Point

The lowest temperature at which vapors arising from the oil will ignite momentarily, when subjected to a flame. (i.e., will flash or "poof").

The vapors will ignite and then go out.

floc point

The temperature at which wax or solids separate in an oil.


High boiling-point, thermally stable organic liquid used as an additive in gasoline to reduce deposits on the undersides of intake valves; also called solvent oil.

See engine deposits


An agglomeration of gas bubbles separated from each other by a thin liquid film which is observed as a persistent phenomenon on the surface of a liquid.


Occurrence of frothy mixture of air and a petroleum product (e.g., lubricant, fuel oil) that can reduce the effectiveness of the product, and cause sluggish hydraulic operation, air binding of oil pumps, and overflow of tanks or sumps. Foaming can result from excessive agitation, improper fluid levels, air leaks, cavitation, or contamination with water or other foreign materials. Foaming can be inhibited with an anti-foam agent. The foaming characteristics of a lubricating oil can be determined by blowing air through a sample at a specified temperature and measuring the volume of foam, as described in test method ASTM D 892.

Foam inhibitor

A substance introduced in a very small proportion to a lubricant or a coolant to prevent the formation of foam due to aeration of the liquid, and to accelerate the dissipation of any foam that may form.

Four-Ball Tester

This name is frequently used to describe either of two similar laboratory machines, the Four-Ball Wear Tester and the Four-Ball EP Tester. These machines are used to evaluate a lubricant's anti-wear qualities, frictional characteristics or load carrying capabilities. It derives its name from the four 1/2 inch steel balls used as test specimens. Three of the balls are held together in a cup filled with lubricant while the fourth ball is rotated against them.


  1. a rubbing, esp. of one object against another.
  2. Mechanics: The resistance to motion of two moving objects or surfaces that touch.
  3. Tribology: The resisting force encouraged at the common boundary between two bodies when, under the action of an external force, one body moves or tends to move relative to the other.

[French; Latin frictio pp. of fricare, to rub]

Friction is the resistance to the motion of one surface over another. The amount of friction is dependent on the smoothness of the contacting surfaces, as well as the force with which they are pressed together.

Friction between unlubricated solid bodies is independent of speed and area.

The coefficient of friction is obtained by dividing the force required to move one body over a horizontal surface at constant speed by the weight of the body.

Coefficients of rolling friction (e.g., the motion of a tire or ball bearing) are much less than coefficients of sliding friction (back and forth motion over two flat surfaces).

Sliding friction is thus more wasteful of energy and can cause more wear.

Fluid friction occurs between the molecules of a gas or liquid in motion, and is expressed as shear stress.
Unlike solid friction, fluid friction varies with speed and area.

In general, lubrication is the substitution of low fluid friction in place of high solid-to-solid friction.

Friction is a "system" property, and not a "material" property and depends on many factors that create the "system".

See asperities, tribology.


Form of wear resulting from small-amplitude oscillations or vibrations that cause the removal of very finely divided particles from rubbing surfaces (e.g., the vibrations imposed on the wheel bearings of an automobile when transported by rail car, or on the fifth wheel on tractor trailers). With ferrous metals the wear particles oxidize to a reddish, abrasive iron oxide, which has the appearance of rust or corrosion, and is therefore sometimes called fretting corrosion; other terms applied to this phenomenon are false Brinelling (localized fretting involving the rolling elements of a bearing) and friction oxidation. Fretting can be controlled with lubricants containing molybdenum disulfide.

fretting corrosion

A special case of fretting in which one or more of the surfaces, or the wear particles therefrom, react with their environment. Mechanical wear initiates fretting, then chemical action or "corrosion" results from the exposure of virgin metal surface to the to the air.

fuel-economy oil

Engine oil specially formulated to increase fuel efficiency.
A fuel-economy oil works by reducing the friction between moving engine parts that wastefully consumes fuel energy.

There are only three known and proven means of accomplishing this goal:

  1. by reducing the viscosity of the oil to decrease fluid friction 
  2. by using friction-reducing chemical additives in the oil to prevent metal-to-metal contact, or rubbing friction, between surface asperities
  3. by introducing solid colloidal particles between surface asperities

See Energy Conserving / Energy Conserving II.

fuel injection

Method of introducing fuel into the combustion process as a finely divided spray under pressure through a small nozzle.
Fuel injection is essential to the compression-ignition process of the diesel cycle.

In the majority of newer-model gasoline-powered cars fuel injection has replaced carburetion, largely due to EPA exhaust emission standards; fuel injection improves combustion efficiency, resulting in lower emissions.

The location and design of fuel injectors is somewhat different between diesel and gasoline engines.

In the diesel engine fuel is injected directly into the cylinder or the pre-combustion chamber. Since the injector nozzle intrudes into the cylinder it must be durable and relatively insensitive to deposit formation in the injector passages.

In most gasoline engines, the fuel is injected into the intake manifold leading to the cylinder, either by a single throttle-body injector or by multiple port injectors (one for each cylinder). Gasoline engine port injectors are highly deposit sensitive, due to their extremely narrow passage clearances of only two-thousandths of an inch and their proximity to high combustion temperatures. This deposit sensitivity required gasoline suppliers to develop a new generation of gasoline additives that could keep these passages deposit-free. Diesel engine manufacturers have begun to express interest in diesel fuel additives that can reduce deposits, thereby increasing combustion efficiency and improving emissions control.

Fuel injection offers a number of advantages over carburetion, including:

See carburetor,  engine deposits, internal combustion engine.

full-fluid-film lubrication

Presence of a continuous lubricating film sufficient to completely separate two surfaces, as distinct from boundary lubrication. Full-fluid-film lubrication is normally hydrodynamic lubrication, whereby the oil adheres to the moving part and is drawn into the area between the sliding surfaces, where it forms a pressure, or hydrodynamic, wedge. See ZN/P curve.

A less common form of full-fluid-lubrication is hydrostatic lubrication, wherein the oil is supplied to the bearing area under sufficient external pressure to separate the sliding surfaces.

FZG test

A German gear test for evaluating EP properties.


gasoline (automotive)

blend of light hydrocarbon fractions of relatively high antiknock value. Automotive, or motor, gasoline may consist of the following components: straight-run naphthas, obtained by the primary distillation of crude oil; natural gasoline, which is "stripped", or condensed, out of natural gas; cracked naphthas; reformed naphthas; and alkylate. (See alkylation, catalytic cracking, reforming).

A high-quality gasoline has the following properties:

  1. proper volatility to ensure easy starting and rapid warm-up
  2. clean-burning characteristics to minimize harmful combustion chamber deposits
  3. additives to prevent rust, oxidation, and deposits in carburetors, intake valves and fuel injectors
  4. sufficiently high octane number to prevent engine knock.

gasoline, aviation (avgas)

high-quality gasoline manufactured under stringent controls to meet the rigorous performance and safety requirements of piston-type aircraft engines.

Volatility of aviation gasoline is closely controlled since, in most aircraft engines, excessive volatility can lead to vapor lock. Aviation gasolines generally have lower vapor pressure and a narrower distillation range than automotive gasolines (see distillation test). Aviation gasolines are formulated to resist chemical degradation and to prevent fuel system corrosion. There are two basic grades of aviation gasolines (based on their antiknock value): 80 (80 lean/87 rich) and 100 (100 lean/130 rich). Aviation gasoline has different properties than turbo fuel, which fuels gas-turbine-powered aircraft.



Machine part which transmits motion and force from one rotary shaft to another by means of successively engaging projections, called teeth. The smaller gear of a pair is called the pinion; the larger, the gear. When the pinion is on the driving shaft, the gear set acts as a speed reducer; when the gear drives, the set acts as a speed multiplier. The basic gear type is the spur gear, or straight-tooth gear, with teeth cut parallel to the gear axis. Spur gears transmit power in applications utilizing parallel shafts. In this type of gear, the teeth mesh along their full length, creating a sudden shift in load from one tooth to the next, with consequent noise and vibration. This problem is overcome by the helical gear, which has teeth cut at an angle to the center of rotation, so that the load is transferred progressively along the length of the tooth from one edge of the gear to the other. When the shafts are not parallel, the most common gear type used is the bevel gear, with teeth cut on a sloping gear face, rather than parallel to the shaft. The spiral bevel gear has teeth cut at an angle to the plane of rotation, which, like the helical gear, reduces vibration and noise. A hypoid gear resembles a spiral bevel gear, except that the pinion is offset so that its axis does not intersect the gear axis; it is widely used in automobiles between the engine driveshaft and the rear axle. Offset of the axes of hypoid gears introduces additional sliding between the teeth, which, when combined with high loads, requires a high-quality EP oil. A worm gear consists of a spirally grooved screw moving against a toothed wheel; in this type of gear, where the load is transmitted across sliding, rather than rolling, surfaces, compounded oils or EP oils are usually necessary to maintain effective lubrication.

gear oil (automotive)

Long-life oil of relatively high viscosity for the lubrication of rear axles and some manual transmissions. Most final drives and many accessories in agricultural and construction equipment also require gear oils. Straight (non-additive) mineral gear oils are suitable for most spiral-bevel rear axles (see gear) and for some manual transmissions. Use of such oils is declining, however, in favor of EP (extreme-pressure) gear oils (see EP oil) suitable both for hypoid gears (see gear) and for all straight mineral oil applications. An EP gear oil is also appropriate for off-highway and other automotive applications for which the lubricant must meet the requirements of Military Specification MIL-L-2105D.


(See API gravity)


A soft form of elemental carbon, gray to black, in color. It occurs naturally or is synthesized from coal or other carbon sources. It is used in the manufacture of paints, lead pencils, crucibles, and electrodes, and is also widely used as a lubricant, either alone as a dry lubricant or added to conventional lubricants; both oils and greases.


A lubricant composed of a lubricating fluid, thickened with soap or other material to a solid or semisolid consistency.

A lubricating grease is a colloidal system, in which metallic soaps or other thickening agents are dispersed in, and give structure to, the liquid lubricant.


heat transfer fluid (HTF)

Oil or other liquid medium used for the transfer of heat.

heavy-duty oil (HD)

An oil suitable for use in commercial diesel engine service. Also referred to as HD.

See API Service Categories.

Herschel Demulsibility Number

A number whIch IndIcates the abilIty of an oIl to separate from water under condtttons spectfted by the Herschel Demulstbility Test.

humidity cabinet test

A test used to evaluate the rust-preventing properties of metal preservatives under conditions of high humIdIty (ASTM Method D 1748).

hydraulic fluid (HF)

Fluid serving as the power transmission medium in a hydraulic system. The most commonly used fluids are petroleum oils, synthetic lubricants, oil-water emulsions, and water-glycol mixtures. The principal requirements of a premium hydraulic fluid are proper viscosity, high viscosity index, anti-wear protection (if needed), good oxidation stability, adequate pour point, good demulsibility, rust inhibition (see rust inhibitor), resistance to foaming, and compatibility with seal materials. Anti-wear oils are frequently used in compact, high-pressure, and high-capacity pumps that require extra lubrication protection. Certain synthetic lubricants and water-containing fluids are used where fire resistance is needed. Synthetic lubricants also are used in extreme-temperature conditions.


A compound containing only hydrogen and carbon. The simplest hydrocarbons are gases at ordinary temperatures; but with increasing molecular weight, they change to the liquid form and, finally, to the solid state. They form the principal constituents of petroleum.

hydrocarbon (HC) emissions

Substances considered to be atmospheric pollutants because the more reactive hydrocarbons (e.g., aromatics) undergo a photochemical reaction with nitrogen oxides (NOx) to form oxidants, components of smog that can cause eye irritation and respiratory problems. Motor vehicles account for about one-third of man-made hydrocarbon emissions, although automotive emission controls are reducing this amount. The greatest portion of total atmospheric hydrocarbons is from natural sources, such as pine trees.

Up to 20% of Heavy Hydrocarbon exhaust emissions are generated by Motor Oils.

See catalytic converter


refining process in which middle and heavy distillate fractions are cracked (broken into smaller molecules) in the presence of hydrogen at high pressure and moderate temperature to produce high-octane gasoline, turbo fuel components, and middle distillates with good flow characteristics and cetane ratings. The process is a combination of hydrogenation and cracking.

See distillation.

hydrodynamic (fluid film) lubrication

An oil film which provides a pressure equal to the load. This pressure enables the moving parts to float on a layer of lubricant.


The chemical addition ot hydrogen to a material. In non-destructive hydrogenation, hydrogen is added to a molecule only if, and where, unsaturation with respect to hydrogen exists.

In destructive hydrogenation, the operation is carried out under conditions which result in rupture of some of the hydrocarbon chains (cracking); hydrogen is added where the chain breaks have occurred.

hypoid gears

Gears in which the pinion axis intersects the plane of the ring gear at a point below the ring-gear axle and above the outer edge of the ring gear, or above the the ring-gear axle and below the outer edge of the ring gear.

Hypoid gear lubricant

A gear lubricant, having extreme pressure characteristics suitable for use with hypoid gears as found, for example, in the differentials of motor vehicles.



The straight-4 or inline-4 is an internal combustion engine with four cylinders aligned in one row. This straight engine configuration is the most common in cars with a displacement up to 2.5 litres.

The straight-4 engine is not a balanced configuration and while this is tolerable in a small, low-displacement, low-power configuration the vibrations get worse with increasing size.


The Independent Lubricant Manufacturers Association (ILMA) is a trade association of businesses engaged in compounding, blending, formulating, packaging, marketing, and distributing lubricants.


The International Lubricant Standardization and Approval Committee (ILSAC) is a joint committee of AAMA and JAMA members that assists in the development of new minimum oil performance standards.


A substance in a petroleum product which prevents or retards undesirable chemical changes from taking place in the product, or in the condition of the equipment in which the product is used. Commonly used inhibitors are used to prevent or retard oxidation or corrosion.

internal combustion engine

Heat engine driven directly by the expansion of combustion gases, rather than by an externally produced medium, such as steam. Basic versions of the internal combustion engine are: gasoline engine and gas engine (spark ignition), diesel engine (compression ignition), and gas turbine (continuous combustion). Diesel compression-ignition engines are more fuel-efficient than gasoline engines because compression ratios are higher, and because the absence of air throttling improves volumetric efficiency. Gasoline, gas (natural gas, propane), and diesel engines operate either on a four-stroke cycle (Otto cycle) or a two-stroke cycle.

Most gasoline engines are of the four-stroke type, with operation as follows:

  1. intake - piston moves down the cylinder, drawing in a fuel-air mixture through the intake valve
  2. compression - all valves closed, piston moves up, compressing the fuel-air mixture, and spark ignites mixture near top of stroke
  3. power - rapid expansion of hot combustion gases drives piston down, all valves remain closed
  4. exhaust - exhaust valve opens and piston returns, forcing out spent gases

The diesel four-stroke cycle differs in that only air is admitted on the intake stroke, fuel is injected at the top of the compression stroke, and the fuel-air mixture is ignited by the heat of compression rather than by an electric spark.

The four-stroke-cycle engine has certain advantages over a two-stroke, including higher piston speeds, wider variation in speed and load, cooler pistons, no fuel lost through the exhaust, and lower fuel consumption.

The two-stroke cycle eliminates the intake and exhaust strokes of the four-stroke cycle. As the piston ascends, it compresses the charge in the cylinder, while simultaneously drawing a new fuel-air charge into the crankcase, which is air-tight. (In the diesel two-stroke cycle, only air is drawn in; the fuel is injected at the top of the compression stroke.) After ignition, the piston descends on the power stroke, simultaneously compressing the fresh charge in the crankcase. Toward the end of the power stroke, intake ports in the piston skirt admit a new fuel-air charge that sweeps exhaust products from the cylinder through exhaust ports; this means of flushing out exhaust gases is called "scavenging". Because the crankcase is needed to contain the intake charge, it cannot double as an oil reservoir. Therefore, lubrication is generally supplied by oil that is pre-mixed with the fuel. An important advantage of the two-stroke-cycle engine is that it offers twice as many power strokes per cycle and, thus, greater output for the same displacement and speed. Because two-stroke engines are light in relation to their output, they are frequently used where small engines are desirable, as in chain saws, outboard motors, and lawn mowers.

Many commercial, industrial, and railroad diesel engines are also of the two-stroke type.

Gas turbines differ from conventional internal combustion engines in that a continuous stream of hot gases is directed at the blades of a rotor. A compressor section supplies air to a combustion chamber into which fuel is sprayed, maintaining continuous combustion. The resulting hot gases expand through the turbine unit, turning the rotor and driveshaft.

See fuel injection


Institute of Petroleum.


International Standards Organization

This organization which is worldwide in scope sets standards and classifications for lubricants. An example is the ISO viscosity grade system.

ISO viscosity classification system

International system, approved by the International Standards Organization (ISO), for classifying industrial lubricants according to viscosity.

Each ISO viscosity grade number designation corresponds to the mid-point of a viscosity range expressed in centistokes (cSt) at 40°C.

For example:

Lubricant with an ISO grade of 32 has a viscosity within the range of 28.8 - 35.2 cSt, the mid-point of which is 32. (see Table below)

ISO viscosity grade number

viscosity range expressed in centistokes (cSt) at 40°C

ISO number Mid-Point Minimum Maximum
2 2.2 1.98 2.42
3 3.2 2.88 3.52
5 4.6 4.14 5.06
7 6.8 6.12 7.48
10 10 9.0 11.0
15 15 13.5 16.5
22 22 19.8 24.2
32 32 28.8 35.2
46 46 41.4 50.6
68 68 61.2 74.8
100 100 90 110
150 150 135 165
220 220 198 242
320 320 288 352
460 460 414 506
680 680 612 748
1000 1000 900 1100
1500 1500 1350 1650


Molecule having the same molecular formula as another molecule, but having a different structure and, therefore, different properties. As the carbon atoms in a molecule increase, the number of possible combinations, or isomers, increases sharply.

For example, octane, an 8-carbon-atom molecule, has 18 isomers; decane, a 10-carbon-atom molecule, has 75 isomers.


An isomer of octane (C8h28) having very good antiknock properties. With a designated octane number of 100, isooctane is used as a standard for determining the octane number of gasolines.


Branched isomer of a straight-chain paraffin molecule.


Pertaining to the conduct of a process or operation of equipment under conditions of constant temperature. Heat is neither generated nor absorbed by the process.



The Japan Automobile Manufacturers Association (JAMA) is a trade association that represents automobile manufacturers headquartered in Japan.


Japanese Automobile Standards Organization (JASO) is comprised of automobile and truck manufacturers, oil and oil additive companies, and government authorities.


Japanese Industrial Standards


kinematic viscosity

absolute viscosity of a fluid divided by its density at the same temperature of measurement. It is the measure of a fluid's resistance to flow under gravity, as determined by test method ASTM D 445. To determine kinematic viscosity, a fixed volume of the test fluid is allowed to flow through a calibrated capillary tube (viscometer) that is held at a closely controlled temperature. The kinematic viscosity, in centistokes (cSt), is the product of the measured flow time in seconds and the calibration constant of the viscometer.

See viscosity.



  1. any substance reducing friction by providing a smooth film as a covering over parts that move against each other; lubricating
  2. a substance for reducing friction in this way, as oil or grease

[Latin lubricans, prp.: see lubricate]

lubricate, lubricated, lubricating
  1. to make slippery or smooth
  2. to apply a lubricant to
  3. to serve as a lubricant

lubrication, lubricative

[< Latin lubricatus, pp. of lubricare, to make smooth or slippery < lubricus, smooth, slippery]

lubricity, lubricities

  1. slipperiness; smoothness; esp., effectiveness as a lubricant as indicated by this quality
  2. trickiness; shiftiness

lubricious or lubricous

[French lubricité < Latin lubricitas]

Ability of an oil or grease to lubricate; also, called film strength.

Lubricity can be enhanced by additive treatment.


Having a strong affinity for, and stabilized by, the liquid dispersing medium: said of a colloidal material. Also lyophile

[lyo- < Greek lyein, to loose + -phil + -ic]


Having little affinity for the liquid dispersing medium: said of a colloidal material

[lyo- (see lyophilic) + -phob(e) + -ic]



On December 16, 1992, the Motor V Manufacturers Association of the United States (MVMA) changed its name to the American Automobile Manufacturers Association (AAMA).


Refers to the marketing organization responsible for the integrity of a brand name and the representation of the branded product in the marketplace.


A light, odorless, flammable gas (CH4); the chief constituent of natural gas.

micron, -microns or -micra

A unit of linear measure equal to one millionth of a meter, or one thousandth of a millimeter

[Modern Latin < Greek mikron, neut. of mikros, small, minute]

Mineral oil

Oil derived from mineral sources, notably petroleum.

mineral spirits

naphthas of mixed hydrocarbon composition and intermediate volatility, within the boiling range of 149°C (300°F) to 204°C (400°F) and with a flash point greater than 38°C (100°F); widely used as solvents or thinners in the manufacture of cleaning products, paints, lacquers, inks, and rubber. Also used uncompounded for cleaning metal and fabrics.

molybdenum disulfide (moly)

A dark green to black, lustrous powder (MoS2) that serves as a dry-film lubricant in certain high-temperature and high-vacuum applications. It is also used in the form of pastes to prevent scoring when assembling press-fit parts, and as an additive to impart residual lubrication properties to oils and greases.

Molybdenum disulfide is often called moly or molysulfide.

See fretting


'Monograde' (single grade) is a term used to describe an oil when its viscosity falls within the limits specified for a single SAE number.(SAE Standard J300)

Motor oil

A type of liquid oil used for lubrication in various kinds of motors, especially internal combustion engines. Other benefits from using motor oil include cooling by carrying heat away from moving engine parts and often include cleaning and corrosion inhibition in internal combustion engines. The major fraction of the majority of motor oils is derived from crude oil (see Petroleum).


'Multigrade' is a term used to describe an oil for which the viscosity/ temperature characteristics are such that its low temperature and high temperature viscosities fall within the limits of two different SAE numbers. (SAE Standard J300)



Generic, loosely defined term covering a range of light petroleum distillates (see distillation). Included in the naphtha classification are: gasoline blending stocks, mineral spirits, and a broad selection of petroleum solvents. In refining, the term light crude naphtha (LCN) usually refers to the first liquid distillation fraction, boiling range 32° to 100°C (90° to 175°F), while heavy crude naphtha is usually the second distillation fraction, boiling range 163° to 218°C (325° to 425°F).


One of a group of cyclic hydrocarbons, also termed cycloparaffins or cycloalkanes.
The general formula for naphthenes is CnH2n

Naphthenic lubricating oils have low pour points, owing to their very low wax content, and good solvency properties.

See saturated hydrocarbon.

Newtonian fluid

Fluid, such as a straight mineral oil, whose viscosity does not change with rate of flow.

See shear stress

Nitrogen Oxides (NOx)

Nitric Oxide (NO), with minor amounts of nitrogen dioxide (NO2). NOx is formed whenever fuel is burned at high temperatures in air, from nitrogen in the air as well as in the fuel. Motor vehicles and stationary combustion sources (furnaces and boilers) are the primary man-made sources, although automotive emission controls are reducing the automobile's contribution. Natural emissions of NOx arise from bacterial action in the soil. NOx can react with hydrocarbons to produce smog.

non-Newtonian fluid

Fluid, such as a grease or a polymer-containing oil (e.g., multi-grade oil), in which shear stress is not proportional to shear rate.

See Brookfield viscosity


National Lubricating Grease Institute

NLGI Number

One of a series of numbers classifying the consistency range of lubricating greases.
The NLGI Numbers are based on the ASTM cone penetration number.
The grades are in order of increasing consistency (hardness)

NLGI Grease Classifications

The following table shows the worked penetration values for the various NLGI grades of grease:

NLGI  Number ASTM  Worked Penetration*
000 445-475
00 400-430
0 355-385
1 310-340
2 265-295
3 220-250
4 175-205
5 130-160
6 85-115

* ASTM Worked Penetration in millimeters at standard test temperature of  77°F ±1°  (25°C ±0.5° )

normal paraffin

hydrocarbon consisting of unbranched molecules in which any carbon atom is attached to no more than two other carbon atoms; also called straight chain paraffin and linear paraffin.

See isoparaffin, paraffin.


octane number

Expression of the antiknock properties of a gasoline, relative to that of a standard reference fuel. There are two distinct types of octane number measured in the laboratory: Research Octane Number (RON) and Motor Octane Number (MON), determined in accordance with ASTM D 2699 and D 2700, respectively. Both the RON and MON tests are conducted in the same laboratory engine, but RON is determined under less severe conditions, and is therefore numerically greater than MON for the same fuel. The average of the two numbers - (RON + MON)/2 - is commonly used as the indicator of a gasoline's road antiknock performance. The gasoline being tested is run in a special single-cylinder engine, whose compression ratio can be varied (the higher the compression ratio, the higher the octane requirement). The knock intensity of the test fuel, as measured by a knockmeter, is compared with the knock intensities of blends of isooctane (assigned a knock rating of 100) and heptane (with a knock rating of zero), measured under the same conditions as the test fuel. The percentage, by volume, of the isooctane in the blend that matches the characteristics of the test fuel is designated as the octane number of the fuel. For example, if the matching blend contained 90% isooctane, the octane number of the test fuel would be 90. In addition to the laboratory tests for RON and MON, there is a third method, Road Octane Number, which is conducted in a specially equipped test car by individuals trained to hear trace levels of engine knock.

See antiknock compounds


Original Equipment Manufacturer

oiliness agent

polar compound used to increase the lubricity of a lubricating oil and aid in preventing wear and scoring under conditions of boundary lubrication.


Any of a series of unsaturated, relatively unstable hydrocarbons characterized by the presence of a double bond between two carbon atoms in its structure, which is commonly straight-chain or branched. The double bond is chemically active and provides a focal point for the addition of other reactive elements, such as oxygen. Due to their ease of oxidation, olefins are undesirable in petroleum solvents and lube oils. Examples of olefins are: ethylene and propylene.

See unsaturated hydrocarbon.


The chemical combination of a substance with oxygen. All petroleum products are subject to oxidation, with resultant degradation of their composition and performance. The process is accelerated by heat, light, metal catalysts (e.g., copper, iron), and the presence of water, acids, or solid contaminants. The first reaction products of oxidation are organic peroxides. Continued oxidation catalyzed by peroxides, forms alcohols, aldehydes, ketones, and organic acids, which can be further oxidized to form high-molecular-weight, oil-insoluble polymers; these settle out as sludges, varnishes, and gums that can impair equipment operation. The organic acids formed from oxidation are corrosive to metals. Oxidation resistance of a product can be improved by careful selection of basestocks (paraffins have greater oxidation resistance than naphthenes), special refining methods, and addition of oxidation inhibitors. Also, oxidation can be minimized by good maintenance of oil and equipment to prevent contamination and excessive heat.

See engine depositsoxidation stability.

oxidation inhibitor

Substance added in small quantities to a petroleum product to increase its oxidation resistance, thereby lengthening its service or storage life; also called anti-oxidant.

An oxidation inhibitor may work in one of three ways:

  1. by combining with and modifying peroxides (initial oxidation products) to render them harmless
  2. by decomposing the peroxides
  3. by rendering an oxidation catalyst (metal or metal ions) inert.

oxidation stability

Resistance of a petroleum product to oxidation; hence, a measure of its potential service or storage life. There are a number of ASTM tests to determine the oxidation stability of a lubricant or fuel, all of which are intended to simulate service conditions on an accelerated basis. In general, the test sample is exposed to oxygen or air at an elevated temperature, and sometimes to water or catalysts (usually iron or copper). Depending on the test, results are expressed in terms of the time required to produce a specified effect (such as a pressure drop), the amount of sludge or gum produced, or the amount of oxygen consumed during a specified period.



Specific type of olefin that is used as a base stock in some synthetic lubricants.
poly-alpha-olefin (or poly-α-olefin, sometimes abbreviated as PAO), is a polymer made by polymerizing an alpha-olefin. An alpha-olefin (or α-olefin) is an alkene where the carbon-carbon double bond starts at the α-carbon atom, i.e. the double bond is between the #1 and #2 carbons in the molecule.


hydrocarbon identified by saturated straight (normal) or branched (iso) carbon chains; also called an alkane. The generalized paraffinic molecule can by symbolized by the formula CnH2n+2. Paraffins are relatively non-reactive and have excellent oxidation stability.

In contrast to naphthenic (see naphthene) oils, paraffinic lube oils have relatively high wax content and pour point, and generally have a high viscosity index (V.I.).

Paraffinic solvents are generally lower in solvency than naphthenic or aromatic solvents.

See normal paraffin, isoparaffin, saturated hydrocarbon.


Pollutants (e.g., smoke particles, metallic ash); in sufficient concentrations, particulates can be a respiratory irritant. Primary sources of man-made particulate emissions are industrial process losses (e.g., from cement plants) and stationary combustion sources. Motor vehicles contribute a relatively minor amount of particulates however Diesel Engines generate much more perticulates in comparison to Gasoline fueled engines.


Passenger Car Motor Oils (PCMOs) refer to engine oils for passenger cars, light-duty trucks, and similar vehicles (see also engine oils).


Consistency of a lubricating grease, expressed as the distance in millimeters that a standard needle or cone penetrates vertically into a sample of the material under known conditions of loading, time and temperature.


Pny chemical derived from crude oil, crude products, or natural gas.

A petrochemical is basically a compound of carbon and hydrogen, but may incorporate many other elements. Petrochemicals are used in the manufacture of numerous products such as synthetic rubber, synthetic fibers (such as nylon and polyester), plastics, fertilizers, paints, detergents, and pesticides.


From Latin Petra(Rock) and Oleum (Oil) therefore meaning "Rock Oil " the term is normally applied to crude oil and commonly used to describe products made from "Crude Oil".

piston engine

A reciprocating engine, also often known as a piston engine, is an engine that utilizes one or more pistons in order to convert pressure into a rotating motion.

The most common form of reciprocating engines use the burning of gasoline or diesel fuel to provide pressure. There may be one or more pistons. Each piston is located inside a cylinder, into which a fuel and air mixture is introduced, and then ignited. As the Air-Fuel mixture burns, the now hot gases expand, pushing the piston away. The linear movement of the piston is converted to a circular movement via a connecting rod and a crankshaft. These engines are known collectively as internal-combustion engines, although internal-combustion engines do not necessarily contain pistons.

PNA (polynuclear aromatic)

Any of numerous complex hydrocarbon compounds consisting of three or more benzene rings in a compact molecular arrangement.

Some types of PNA's are known to be carcinogenic (cancer causing). PNA's are formed in fossil fuel combustion and other heat processes, such as catalytic cracking. They can also form when foods or other organic substances are charred. PNA's occur naturally in many foods, including leafy vegetables, grain cereals, fruits, and meats.

polar compound

a chemical compound whose molecules exhibit electrically positive characteristics at one extremity and negative characteristics at the other. Polar compounds are used as additives in many petroleum products. Polarity gives certain molecules a strong affinity for solid surfaces; as lubricant additives (oiliness agents), such molecules plate out to form a tenacious, friction-reducing film. Some polar molecules are oil-soluble at one end and water-soluble at the other end; in lubricants, they act as emulsifiers, helping to form stable oil-water emulsions. Such lubricants are said to have good metal-wetting properties. Polar compounds with a strong attraction for solid contaminants act as detergents in engine oils by keeping contaminants finely dispersed.


Product of polymerization (very large molecule).

Substance formed by the linkage (polymerization) of two or more simple, unsaturated molecules (see unsaturated hydrocarbon), called monomers, to form a single heavier molecule having the same elements in the same proportions as the original monomers; i.e. each monomer retains its structural identity.

Polymer may be liquid or solid; solid polymers may consist of millions of repeated linked units.

Polymer made from two or more dissimilar monomers is called a copolymer.

Copolymer composed of three different types of monomers is a terpolymer.

Natural rubber and synthetic rubbers are examples of polymers.

Polymers are commonly used as viscosity index improvers in multi-grade oils.


The combination, usually under controlled conditions of temperature and pressure in the presence of a catalyst, of two or more unsaturated organic molecules to form a more complex molecule. The products obtained are known as polymers.

Typical polymers range from light liquids to rubber like materials.

In petroleum refining, polymerization refers to the combination of light, gaseous hydrocarbons, usually olefins, into high-molecular-weight hydrocarbons that are used in manufacturing motor gasoline and aviation fuel.

The product formed by combining two identical olefin molecules is called a dimer, and by three such molecules, a trimer.

See polymer.

polyol ester

Synthetic lubricant base, formed by reacting fatty acids with a polyol (such as a glycol) derived from petroleum. Properties include good oxidation stability at high temperatures and low volatility. Used in formulating lubricants for turbines, compressors, jet engines, and automotive engines.


polymer derived by polymerization of relatively simple olefins.

Polyethylene and polyisoprene are important polyolefins.

positive crankcase ventilation (PCV)

A system for removing blow-by gases from the crankcase and returning them, through the carburetor intake manifold, to the combustion chamber, where the recirculated hydrocarbons are burned, thus reducing hydrocarbon emissions to the atmosphere.
A PCV valve, operated by engine vacuum, controls the flow of gases from the crankcase. PCV systems have been standard equipment in all U.S. cars since 1963, replacing the simpler vent, or breather, that allowed crankcase vapors to be emitted to the atmosphere.

See emissions (automotive)

pour point

The lowest temperature at which oil will pour or flow when it is chilled without disturbance under definite conditions (ASTM Method D 97). It gives an indication of the lowest operating temperature for which particular oil is suitable.

pour point depressant (PPD)

A lubricating oil additive which lowers the pour point of an oil by reducing the tendency of the wax, suspended in the oil, to form crystals or a solid mass in the oil, thus preventing flow.
Also called pour depressor or pour point depressor.

pour stability

The ability of a pour depressed oil to maintain its original ASTM pour point when subjected to long term storage at low temperature aproximating winter conditions.

process oil

Oil not used for lubrication, but as a component of another material, or as a carrier of other products, such as additives.

process stream

General term applied to a partially finished petroleum product moving from one refining stage to another; less commonly applied to a finished petroleum product.


Gaseous paraffinic hydrocarbon (C3H8) present in natural gas and crude oil; also termed, along with butane, liquefied petroleum gas (LPG).

Power Steering Fluid (PSF)

Hydraulic fluid formulated to be used in Automotive Power Steering Systems.

pumpability (lubricating grease)

The ability of a lubricating grease to flow under pressure through the line, nozzle and fitting of a grease dispensing system.



Atom or group of atoms with one or more unpaired electrons. A group of atoms functioning as a radical acts as a single atom, remaining intact during a chemical reaction.

rapeseed oil (blown rapeseed oil)

Fatty oil used for compounding petroleum oil.

See compounded oil

Redwood viscosity

Method for determining the viscosity of petroleum products; it is widely used in Europe, but has limited use in the U.S.
The method is similar to Saybolt Universal viscosity; viscosity values are reported as "Redwood seconds."


Rust & Oxidation inhibited

A term applied to highly refined industrial lubricating oils formulated for long service in circulating lubrication systems, compressors, hydraulic systems, bearing housing, gear boxes, etc.

The finest R&O oils are often referred to as turbine oils.


Series of processes for converting crude oil and its fractions to finished petroleum products. Following distillation, a petroleum fraction may undergo one or more additional steps to purify or modify it.

These refining steps include:

Refined lube oils may be blended with other lube stocks, and additives may be incorporated, to impart special properties; refined naphthas may be blended with alkylates, cracked stock or reformates to improve octane number and other properties of gasolines.


Solid or semi-solid materials, light yellow to dark brown, composed of carbon, hydrogen, and oxygen. Resins occur naturally in plants, and are common in pines and firs, often appearing as globules on the bark. Synthetic resins, such as polystyrene, polyesters, and acrylics, are derived primarily from petroleum. Resins are widely used in the manufacture of inks, lacquers, varnishes, plastics, adhesives, and rubber.

rust inhibitor

Type of corrosion inhibitor used in lubricants to protect the lubricated surfaces against rusting.

See R&O.

rust preventive

Compound for coating metal surfaces with a film that protects against rust; commonly used for the preservation of equipment in storage. The base material of a rust preventive may be a petroleum oil, solvent, wax, or asphalt, to which a rust inhibitor is added. A formulation consisting largely of a solvent and additives is commonly called a thin-film rust preventive because of the thin coating that remains after evaporation of the solvent. Rust preventives are formulated for a variety of conditions of exposure, e.g., short-time "in-process" protection, indoor storage, exposed outdoor storage, etc.



The Society of Automotive Engineers (SAE) is an engineering society founded to develop, collect, and disseminate knowledge of mobility technology.

While keeping the SAE acronym, it has been renamed to SAE International, and engineers in all modes of transportation are now alowed and encouraged to join the society.

Web Link:

saturated hydrocarbon

hydrocarbon with the basic formula CnH2n+2; it is saturated with respect to hydrogen and cannot combine with the atoms of other elements without giving up hydrogen. Saturates are more chemically stable than unsaturated hydrocarbons.

Saybolt Furol viscosity

The efflux time in seconds required for 60 milliliters of a petroleum product to flow through the calibrated orifice of a Saybolt Furol viscometer, under carefully controlled temperature, as prescribed by test method ASTM D 88.
The method differs from Saybolt Universal viscosity only in that the viscometer has a larger orifice to facilitate testing of very viscous oils, such as fuel oil (the word "Furol" is a contraction of "fuel and road oils").

The Saybolt Furol method has largely been supplanted by the kinematic viscosity method.

See viscosity

Service Category

A Service Category is an alphanumeric code developed by API to specify a level of performance defined by ASTM D 4485 and SAE Standard J183. As new Service Categories are developed, new alphanumeric codes may be assigned.


Distress marks on sliding metallic surfaces in the form of long, distinct scratches in the direction of motion. Scoring is an advanced stage of scuffing.

See four-ball method, Timken EP test.


Localized distress marks on sliding metallic surfaces, appearing as a matt-finished area rather than as individual score marks.

See scoring.

shear rate

Rate at which adjacent layers of a fluid move with respect to each other, usually expressed as reciprocal seconds (also see shear stress).

shear stress

Frictional force overcome in sliding one "layer" of fluid along another, as in any fluid flow.

The shear stress of a petroleum oil or other Newtonian fluid at a given temperature varies directly with shear rate (velocity).

The ratio between shear stress and shear rate is constant; this ratio is termed viscosity.

The higher the viscosity of a Newtonian fluid, the greater the shear stress as a function of rate of shear. In a non-Newtonian fluid - such as a grease or a polymer-containing oil (e.g.,multi-grade oil) - shear stress is not proportional to the rate of shear.

A non-Newtonian fluid may be said to have an apparent viscosity, a viscosity that holds only for the shear rate (and temperature) at which the viscosity is determined.

See Brookfield viscosity.


In gasoline engines, a black emulsion of water, other combustion by-products, and oil formed primarily during low-temperature engine operation. Sludge is typically soft, but can polymerize to very hard substance. It plugs oil lines and screens, and accelerates wear of engine parts. Sludge deposits can be controlled with a dispersant additive that keeps the sludge constituents finely suspended in the oil.

See engine deposits.


A colloidal dispersion in a liquid

[< (hydro)sol]


Compound with a strong capability to dissolve a given substance.

The most common petroleum solvents are mineral spirits, xylene, toluene, hexane, heptane, and naphthas. Aromatic-type solvents have the highest solvency for organic chemical materials, followed by naphthenes and paraffins.

In most applications the solvent disappears, usually by evaporation, after it has served its purpose. The evaporation rate of a solvent is very important in manufacture: rubber cements often require a fast-drying solvent, whereas rubber goods that must remain tacky during processing require a slower-drying solvent. Solvents have a wide variety of industrial applications, including the manufacture of paints, inks, cleaning products, adhesives, and petrochemicals. Other types of solvents have important applications in refining.

solvent extraction

refining process used to separate reactive components (unsaturated hydrocarbons) from lube distillates in order to improve the oil's oxidation stability, viscosity index (V.I.), and response to additives. Commonly used extraction media (solvents) are: phenol, N-methylpyrrolidone (NMP), furfural, liquid sulfur dioxide, and nitrobenzene. The oil and solvent are mixed in an extraction tower, resulting in the formation of two liquid phases: a heavy phase consisting of the undesirable unsaturates (see unsaturated hydrocarbon) dissolved in the solvent, and a light phase consisting of high quality oil with some solvent dissolved in it. The phases are separated and the solvent recovered from each by distillation. The unsaturates portion, or extract, while undesirable in lubricating oils, is useful in other applications, such as rubber extender oils (rubber oil) and plasticizer oils.

sour crude

crude oil containing appreciable quantities of hydrogen sulfide or other sulfur compounds, as contrasted to sweet crude.


hydrocarbon in which a hydrogen atom has been replaced with the highly polar (SO2OX) group, where X is a metallic ion or alkyl radical.

Petroleum sulfonates are refinery by-products of the sulfuric acid treatment of white oils. Sulfonates have important applications as emulsifiers and chemical intermediates in petrochemical manufacture. Synthetic sulfonates can be manufactured from special feedstocks rather than from white oil basestocks.

See polar compound


Common natural constituent of petroleum and petroleum products. While certain sulfur compounds are commonly used to improve the EP, or load-carrying, properties of an oil (see EP oil), high sulfur content in a petroleum product may be undesirable as it can be corrosive and create an environmental hazard when burned (see sulfur oxide). For these reasons, sulfur limitations are specified in the quality control of fuels, solvents, etc. Sulfur content can be determined by ASTM tests.

Sulfur oxide

Major atmospheric pollutant, predominantly sulfur dioxide (SO2) with some sulfur trioxide (SO33), primarily emitted from stationary combustion sources (furnaces and boilers). Sulfur oxides are formed whenever fuels containing sulfur are burned.

SO2 is also present in the air from natural land and marine fermentation processes.


Saybolt Universal Seconds. A measure of lubricating oil viscosity in the oil industry.
The measuring apparatus is filled with specific quantity of oil or other fluid and its flow time through standatized offrice is measured in Seconds.

Fast flowing fluids (low viscosity) will have low value; Slow flowing fluids (high viscosity) will have high value.

sweet crude

Crude oil containing little or no sulfur.

See sour crude.


  1. the simultaneous action of separate agencies which, together, have greater total effect than the sum of their individual effects.
  2. the combined or correlated action of different parts working together.
  3. In relation to lubricants the beneficial reaction between base oil and additive or between two or more additives.

[Modern Latin synergismus< Greek synergos, working together]

See synergy


  1. combined or cooperative action or force
  2. synergism


[Modern Latin synergia < Greek joint work < synergein, to work together < syn-, together + ergon, work ]


  1. of, involving, or using synthesis
  2. produced by synthesis; specially: produced by chemical synthesis, rather than of natural origin
  3. not real or genuine; artificial [synthetic lubricant]
  4. something synthetic; specially, a substance produced by chemical synthesis
  5. Man-made, not occuring in nature

[French synthétique < Greek synthetikos]

synthetic oils

Oils produced by synthesis (chemical reaction) rather than by extraction or refinement.
Many (but not all) synthetic oils offer immense advantages in terms of high temperature stability and low temperature fluidity, but are more costly than mineral oils.
Major advantage of all synthetic oils their chemical unformity that does not significianly vary from batch to batch.


tackiness agent

An additive used to increase the adhesive properties of a lubricant, improve retention, and prevent dripping and splattering.


A descriptive term applied to lubricating oils and greases which appear particularly sticky or adhesive.

TAN (Total Acid Number)

The quantity of base, expressed in terms of the equivalent number of milligrams (mg) of Potasium Hydroxide, that is required to titrat the strong acid constituents present in 1 gram (g) of oil sample. (ASTM Method D 644 or D 974).

TBN (Total Base Number)

The quantity of acid, expressed in terms of the equivalent number of milligrams (mg) of Potasium Hydroxide, that is required to titrat the strong base constituents present in 1 gram (g) of oil sample. (ASTM Method D 644 or D 974).

Teflon (PTFE)

The original form of Teflon® is polytetrafluoroethylene, or PTFE. The molecular structure of Teflon® is based on a chain of carbon atoms, the same as all polymers. Unlike some other fluoropolymers, in Teflon® this chain is completely surrounded by fluorine atoms. The bond between carbon and fluorine is very strong, and the fluorine atoms shield the vulnerable carbon chain.
This unusual structure gives Teflon® its unique properties.
In addition to its extreme slipperiness, it is inert to almost every known chemical.

*Teflon® is a registered trademark of the DuPont Company for many of its fluorine-based products including fluoropolymer resins, films, coatings, additives and other products.


The property of a grease or some gels to decrease in cosnsistency when subjected to a shear stress and return to original consistency when the stress is removed.

Timken EP tester

One of may laboratory machines used in determining the load carrying ability and capacity of oils and greases; it measures the extreme-pressure properties of a lubricating oil (see EP oil).

In this tester (Timiken Machine), an outer race of a roller bearing, which is lubricated by the product under test, is rotated against a steel block.
The test continues under increasing load (pressure) until a measurable wear scar is formed on the block.

Timken OK load is the highest load under which a lubricant prevents scoring of the steel block by the rotating cup.
This load is the reported value.


Combining form meaning friction.


Science devoted to the study of friction, wear and lubrication between interacting parts, in intimate contact during relative motion, such as gears and bearings.

tribological, tribologist

[ trib(o) = < Greek tribein, to rub- + -logy = ME -logie < Old French < Latin -logia < Greek < logos, word; also science, doctrine, or theory of]


ultraviolet absorbance

Measurement of the ultraviolet absorption of petroleum products, determined by standardized tests, such as ASTM D 2008. Aromatics absorb more ultraviolet light than do naphthenes and paraffins, and the amount of absorbance can be used as an indication of the amount of aromatics in a product.
Certain polynuclear aromatics (PNA are known carcinogens (cancer-causing substances), with peaks of absorbance generally between 280 and 400 millimicrons. The Food and Drug Administration (FDA) has therefore imposed limits on the amount of ultraviolet absorbance at these wavelengths for materials classified as food additives.
However, not all materials with ultraviolet absorbance at these wavelengths are carcinogenic.

unsaturated hydrocarbon

hydrocarbon lacking a full complement of hydrogen atoms, and thus characterized by one or more double or triple bonds between carbon atoms. Hydrocarbons having only one double bond between adjacent carbon atoms in the molecule are called olefins; those having two double bonds in the molecule are diolefins. Hydrocarbons having alternating single and double bonds between adjacent carbon atoms in a benzene-ring configuration are called aromatics. Hydrocarbons with a triple bond between carbon atoms are called acetylenes. Unsaturated hydrocarbons readily attract additional hydrogen, oxygen, or other atoms, and are therefore highly reactive.

See saturated hydrocarbon, hydrogenation.



It is an internal combustion piston engine with six cylinders in a "V" configuration.
It is the second most common engine configuration in modern cars after the straight-4; it shares with that engine a compactness very suited to the popular front wheel drive layout, and is becoming more popular as car weights increase.

The first V6 was introduced by Italian Lancia on the 1924 Lancia Lambda, but it made little impact. The design was reintroduced by the company in 1950 with the Lancia Aurelia; this time, other manufacturers took note and soon other V6 engines were in use.


  1. Hard, varnish-like coating formed from oil oxidation products, that bakes on to pistons during high-temperature operation of automotive engines and industrial machinery. Varnish can accelerate cylinder wear. Varnish formation can be reduced with the use of a detergent-dispersant and an oxidation inhibitor in the oil. See engine deposits

  2. In ink formation, varnish - composed of resin, solvent, and additives - is the vehicle to which pigment is added to make printing ink.

Vegetable oils

These are derived from a vegetable source.
From pure lubrication considerations, they may be regarded as superior to mineral oils as their chemical nature provides excellent adhesion to metal surfaces due to their inherent polarity.
However, they have relatively poor high temperature stability and are costly.

Examples: castor oil, jojoba oil, sunflower oil, rape seed oil, Olive oil, etc.

VI (Viscosity Index)

An arbitrary scale used to show the magnitude of viscosity changes in lubricating oils with changes in temperature. Oils with low VI number such as VI=0 ("zero") have high dependence of viscosity change on temperature. They thicken quickly with decreasing temperature, and thin out quickly with increasing temperature. Oils with high VI number such as VI=200, will still thicken with decreasing temperature but not as rapidly, and also will thin out with increasing temperature, but again not as much as low VI oil.

VI number can also be "negative"

Tables found in ASTM Method D 2270 are widely used to determine VI number.

However, VI does not tell the whole story -- it only reflects the viscosity/temperature relationship between temperatures of 40°C and 100°C. Two lubricants or base oils with the same VI number may perform dramatically different at low temperatures in the -5°C to - 50°C range.


Device for measuring viscosity; commonly in the form of a calibrated capillary tube through which a liquid is allowed to pass at a controlled temperature in a specified time period.

See kinematic viscosity, Saybolt Universal Viscosity.


The measure of the internal friction or the resistance to flow a liquid.
Low viscosity fluids flow easily (water);
High viscosity fluids pour slowly (molasses, cold honey).

Viscosity is a measurement of a fluid's resistance to flow.
The common metric unit of absolute viscosity is the poise, which is defined as the force in dynes required to move a surface one square centimeter in area past a parallel surface at a speed of one centimeter per second, with the surfaces separated by a fluid film one centimeter thick. For convenience, the centipoise (cp) - one one-hundredth of a poise - is the unit customarily used. Laboratory measurements of viscosity normally use the force of gravity to produce flow through a capillary tube (viscometer) at a controlled temperature. This measurement is called kinematic viscosity.
The unit of kinematic viscosity is the stoke, expressed in square centimeters per second. The more customary unit is the centistoke (cSt) - one one-hundredth of a stoke. Kinematic viscosity can be related to absolute viscosity by the equation:

cSt = cp ÷ fluid density

In addition to kinematic viscosity, there are other methods for determining viscosity, including

Since viscosity varies inversely with temperature, its value is meaningless unless the temperature at which it is determined is reported.

See: viscosity index, viscosity-temperature relationship

Viscosity Index Improver (VII)

Chemical additive that is added to finished lubricants to improve the viscosity index.

Lubricant additive, usually a high-molecular-weight polymer, that reduces the tendency of an oil to change viscosity with temperature. Multi-grade oils, which provide effective lubrication over a broad temperature range, usually contain V.I. improvers.

While Viscosity Index Improvers can enhance viscosity index (VI), they can break down under shear or over time, resulting in diminished performance.

viscosity-temperature relationship

The manner in which the viscosity of a given fluid varies inversely with temperature. Because of the mathematical relationship that exists between these two variables, it is possible to predict graphically the viscosity of a petroleum fluid at any temperature within a limited range if the viscosities at two other temperatures are known. The charts used for this purpose are the ASTM Standard Viscosity-Temperature Charts for Liquid Petroleum Products, available in 6 ranges. If two known viscosity-temperature points of a fluid are located on the chart and a straight line drawn through them, other viscosity-temperature values of the fluid will fall on this line; however, values near or below the cloud point of the oil may deviate from the straight-line relationship.


Possessing viscosity. Frequently used to imply high viscosity.


The degree to which a substance tends to vaporise or evaporate; expression of evaporation tendency.

Liquids with high volatility will loose (by evaporation) high percentage of their weight or volume when heated to specific test temperature (Noack Volatility Test).

The more volatile a petroleum liquid, the lower its boiling point and the greater its flammability. The volatility of a petroleum product can be precisely determined by tests for evaporation rate; also, it can be estimated by tests for flash point and vapor pressure, and by distillation tests.


wax (petroleum)

Any of a range of relatively high-molecular-weight hydrocarbons (approximately C16 to C50, solid at room temperature, derived from the higher-boiling petroleum fractions.

There are three basic categories of petroleum-derived wax:

  1. paraffin (crystalline)
  2. microcrystalline
  3. petrolatum

Paraffin waxes are produced from the lighter lube oil distillates, generally by chilling the oil and filtering the crystallized wax; they have a distinctive crystalline structure, are pale yellow to white (or colorless), and have a melting point range between 48°C (118°F) and 71°C (160°F). Fully refined paraffin waxes are dry, hard, and capable of imparting good gloss.

Microcrystalline waxes are produced from heavier lube distillates and residua (see bottoms) usually by a combination of solvent dilution and chilling. They differ from paraffin waxes in having poorly defined crystalline structure, darker color, higher viscosity, and higher melting points - ranging from 63°C (145°F) to 93°C (200°F). The microcrystalline grades also vary much more widely than paraffins in their physical characteristics: some are ductile and others are brittle or crumble easily. Both paraffin and microcrystalline waxes have wide uses in food packaging, paper coating, textile moisture proofing, candle-making, and cosmetics.

Petrolatum is derived from heavy residual lube stock by propane dilution and filtering or centrifuging. It is microcrystalline in character and semi-solid at room temperature.

There are also heavier grades for industrial applications, such as corrosion preventives, carbon paper, and butcher's wrap. Traditionally, the terms slack wax, scale wax, and refined wax were used to indicate limitations on oil content. Today, these classifications are less exact in their meanings, especially in the distinction between slack wax and scale wax.


The removal of materials from surfaces in relative motion.

Wear inhibitor

An additive which protects the rubbing surfaces against wear, particularly from scuffing, if the hydrodynamic film is ruptured.

white oil

Highly refined straight mineral oil, essentially colorless, odorless, and tasteless. White oils have a high degree of chemical stability. The highest purity white oils are free of unsaturated components (see unsaturated hydrocarbon) and meet the standards of the United States Pharmacopeia (USP) for food, medicinal, and cosmetic applications. White oils not intended for medicinal use are known as technical white oils and have many industrial applications - including textile, chemical, and plastics manufacture - where their good color, non-staining properties, and chemical inertness are highly desirable.

worked penetration

The penetration of a sample of lubricating grease immediately after it has been brought to 77°F and then subjected to 60 stokes in a standard grease worker.
This procedure and the standard grease worker are described in ASTM Method D 217.



aromatic hydrocarbon, C8H10, with three isomers plus ethylbenzene.

It is used as a solvent in the manufacture of synthetic rubber products, printing inks for textiles, coatings for paper, and adhesives, and serves as a raw material in the chemical industry.


yield point

The minimum force required to produce flow of a plastic material.

See plasticity.



A chemical (zinc dialkyl dithiophosphate or zinc diaryl dithiophosphate)

Widely used as an anti-wear additive in engine oils to protect heavily loaded parts, particularly the valve train mechanisms (such as the camshaft and cam followers) from excessive wear. It is also used as an anti-wear agent in hydraulic fluids and certain other products.

ZDDP is also an effective oxidation inhibitor.

Oils containing ZDDP should not be used in engines that employ silver alloy bearings. All car manufacturers now recommend the use of dialkyl ZDDP in engine oils for passenger car service (PCMO).

ZN/P curve

general graphic representation of the equation:

µ = (f) ZN/P

Where µ (the coefficient of friction in a journal bearing) is a function (f) of the dimensionless parameter ZN/P, (viscosity x speed)/pressure. This is the fundamental lubrication equation, in which the coefficient of friction is the friction per unit load, Z the viscosity of the lubricating oil, N the rpm of the journal, and P the pressure (load per unit area) on the bearing. The ZN/P curve illustrates the effects of the three variables (viscosity, speed, and load) on friction and, hence, on lubrication.

See boundary lubrication, full-fluid-film lubrication.

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