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SAE 5W-20 Motor Oil

SAE 5W-20 Motor Oil

Should you use it in your vehicle?

The answer is simple:

You will get at best about 2% better fuel economy, but you may get up to 30% shorter engine life !

The above statement is based on real life experience and in comparison to SAE 5W-30 Motor Oil.


The above introduction has been published back in 2002, when FORD and HONDA were the first two companies installing SAE 5W-20 Motor Oil into few of their vehicles as "Factory Fill".

In case of FORD it was the FORD Focus PZEV, that at that time was available only in California as 2003 Model, and

in case of HONDA it was SAE 0W-20 used only in their first Hybrid the Insight.

Since the original publication of this article on our web, over 101,300 unique visitors have read this page!


In order for you to understand the "shocking" short answer, some lengthy explanation is in order!

One however FIRST needs to understand the evolution of Motor Oil Labeling and what those mysterious Numbers following the "SAE" on Motor Oil Label actually mean!

SAE - What is it ?

The SAE has been the first organization that in June 1911 developed the SAE J300 standard that specifies Engine Oil Viscosity Classification.

The "SAE" then on the caps of glass oil bottles and later on the tops of paper oil cans, does not stand for any magic, it is simply the abbr for "Society of Automotive Engineers".


VISCOSITY Click the Left button for link to web page that explains VISCOSITY in more detail.

Before SAE came up with this scheme to classify oils by their viscosity in simple terms, which hopefully the motoring public could comprehend and easily understands, there was no simple way to tell how oil would behave in automotive engine when "hot".

Back then oils had no W rating, which stands for "Winter". Since cars were seldom driven in winter this was not a real problem. The roads were generally impassable and vehicles usually not capable of starting when temperatures approached freezing.

Therefore the SAE viscosity rating was based on how quickly a specific quantity of motor oil flowed through a test ofrice when heated to operating temperature (100 °C = 212 °F).

The SAE Viscosity Number or "Grade" according to the initial SAE J300 standard was simply an average time in seconds that tested oil would take to flow through the test apparatus.

Since SAE did not want to confuse the public with hundreds of numbers and since the simple test yielded different times for different experimenters, it was decided to make the graduation in steps, rather than in absolute test values.

Therefore the SAE Viscosity Number according to the SAE J300 standard was an "approximation" and NOT an exact measure - and continues to be so even today.


Any oil that took from 5 to 14 seconds to flow would be SAE 10.

Oil that would take 15 to 24 seconds would be labeled as SAE 20.

Oil that took 25 to 34 seconds would be SAE 30.

And so on until SAE 50.

VISCOSITY Click the Left button for link to web page that explains VISCOSITY in more detail.

First SAE J300 Table

In the original SAE J300 specifications there was neither SAE 5 oil nor any SAE 60 oil.

The science of Rheology (The flow of liquids) was not well developed at that time.

Automotive engineers were neither scientists nor physicists.

Therefore it took several years before the SAE J300 "staircase" was translated from time measurement numbers in a crude instrument into a scientific viscosity values for viscosity expressed in Poise.

Not to confuse the motorists, who by then got used to buy motor oils by SAE numbers, the numbering system that by then did not relate to anything comprehensible was maintained - and is still in used today.

Eventually the J300 SAE Standard was also recognized, but not adapted by API (American Petroleum Institute).

Hundreds of Oil producers had thousands of oilcans with SAE numbers on them, and they were already in the market place.

Under such circumstances any introduction of a "new" labeling scheme would have certainly failed, so keeping the "old" non-scientific Motor Oil Labeling convention prevailed and has been maintained till today.

As far as the author of this article could find the oldest Motor Oil SAE Numbering system was as follows:

Flow Test time (seconds)
in Apparatus
Viscosity in CentiStokes
@ 100 °C
10 under 14 4.00 ( 2 - 5)
20 15 to 24 7.45 ( 6 - 8)
30 25 to 34 10.90 ( 9 - 12)
40 35 to 44 14.40 (13 - 16)
50 over 45 19.10 (17 - 21)

The last column is not part of the "original" SAE J300 Viscosity Standard, they are the average viscosity values (and the range) of oils that were typically sold within that specific "SAE Grade".
Using "modern" scientific units for Viscosity both the "average" and "range" in CentiStokes is shown.

The SAE Viscosity Numbers only indicated the oil's ability to flow at the test temperature of 100 °C (212 °F).

The SAE Viscosity Number did not in any way imply suitability for any purpose or quality or performance of the oil that carried such identification.

The test was also performed ONLY on FRESH oil, so no durability or stability was ever implied.

Viscosity Index

During the early days of motoring, the Motor Oils were "pure" petroleum oil with no enhancements in processing. Nor did Motor Oils contain any additives, therefore eventually oil marketers started to label ALL petroleum oils in the market place with the SAE Viscosity Numbering system Numbers, so that consumers could quickly identify what viscosity the oil was when "at engine operating temperature".

This early specification was important for simple reason, because oils sourced from different oil fields and different regions had vastly different viscosity index (which at that time was not yet well defined, although recognized by oil people).

Viscosity Index (VI) is nonscientific arbitrary value that simply represents the slope of inverse relationship of oil viscosity to temperature.

All petroleum will flow slowly at room temperature, and much faster when heated up.

Therefore as the temperature is increased the viscosity is decreased.

That is what is expressed mathematically as inverse relationship.

If one value goes up (temperature), then the other goes down (viscosity).

Some oils although they were thick at room temperature would flow as easily as water when hot, yet others that were not as thick at room temperature would not thin out as much.

This means that two different oils that appeared to have an identical viscosity at room temperature (which was usually the temperature at which the motorist would purchase or pour the oil into the engine), did have totally differing viscosity when heated up.

The early automotive engineers even then recognized the viscosity, as very important quality.

And above all the viscosity when "at operating temperature" or when "hot" was universally agreed to be far more important quality, than the viscosity when the oil was at ambient temperature.

This was especially important since one oil sourced from Gulf Coast, for example, could be thick when cold, yet unable to protect the engine adequately when hot.

By contrast another oil from Pennsylvania, which was lot easier to pour when ambient, would be just right for automotive engine when hot.

The first example of the thick when cold and really thin when hot, was oil with low viscosity index.

VI of ZERO - The thick black Gulf Coast Aromatic crude would behave like this.

The second example of the not so thick when cold and not as thin when hot, would be the oil with high viscosity index. VI of 100 (then thought to be the BEST possible) - The amber oil which came from the oil fields of Pennsylvania and consisting of the paraffin crude that made Pennzoil and Quaker State world famous.

Although the VI (Viscosity Index) was eventually defined by API, it was really not of any concern to SAE and still till today is not part of any SAE specification.

The actual viscosity at differing extremes of engine operation is what Automotive Engineers today agree on as most important specification.

Evolution of SAE J300 Standard

Over the 101 years that the SAE J300 Standard was in effect, number of shortcomings were discovered and the Standard was amended numerous times, and although its evolution is of interest, the discussion of its exact detailed history is far beyond the scope of this article.

However, here is in brief what has happened over the 101 years.

SAE 60 grade was added as the need for thicker oil in aviation and heavy duty engines became apparent.

SAE "W" grades were added in 1952 as it became apparent that engines could not be started in Cold Winter Climatic conditions with some SAE 30 oils. The "Winter" (W) performance was originally defined as viscosity at 0°F or -11.8°C.

SAE 5W and later SAE 0W grades were added as thinner "economy" oils needed to be defined.

Additional test specifications for winter performance were added to "W" requirements as engines frequently failed mechanically in cold climate immediately after initial start, due to oil starvation.

SAE 15W and SAE 25W grades were added to further narrow the performance definitions in Winter Climates.

In 1970's minimum high temperature high shear specifications were added for performance at 150 °C (300 °F), when it became obvious that engines suffered from excessive wear or even seized at high-speed high-temperature operation such as long distance interstate driving or towing in Hot Summer climate.

So the changes to SAE J300 Standard were usually, until very recently, a reaction to "fix" an existing problem with lubricants that caused engine problems in service.
This was either due to viscosity breakdown when hot or failure to flow when cold. In either case, resulting in catastrophic engine failures.

Last few SAE J300 Standard changes were PROACTIVE. They were legislated jointly by the auto and engine manufacturers, as well as, the lubricating oil producers, before any problems in the field occurred. This was based on research tests in the laboratories, and therefore done in anticipation of problems before they had chance to occur.

Many of these specification changes were necessary because today's cars equipped with electronic fuel injection and electronic ignition will start immediately at much lower temperatures, than vehicles made just a decade ago.

Much smaller engines with lower engine oil capacities produce much more power and thus put oil under much greater mechanical as well as thermal stress.

The December 1999 revision of SAE J300 Engine Oil Viscosity Classification Standard is tabulated below:

Revised DEC 1999

SAE Viscosity Grade Cold Cranking Maximum Viscosity
@ Specified Temperature
Cold Pumping Maximum Viscosity
@ Specified Temperature
Hot Viscosity
@ 100 °C Kinematic
Hot/High Shear
@ 150 °C Minimum
0W 6,200 @ -35 °C 60,000 @ -40 °C > 3.8
5W 6,600 @ -30 °C 60,000 @ -35 °C > 3.8
10W 7,000 @ -25 °C 60,000 @ -30 °C > 4.1
15W 7,000 @ -20 °C 60,000 @ -25 °C > 5.6
20W 9,500 @ -15 °C 60,000 @ -20 °C > 5.6
25W 13,000 @ -10 °C 60,000 @ -15 °C > 9.3
20 >5.6 <9.3 2.6
30 >9.3 <12.5 2.9
40 >12.5 <16.3 2.9
40 >12.5 <16.3 3.7
50 >16.3 <21.9 3.7
60 >21.9 <26.1 3.7

The most recent January 2009 revision of SAE J300 Engine Oil Viscosity Classification Standard is tabulated below:

Revised JAN 2009

Low Temperature °C
Cranking Viscosity
(mPa∙s) Max (CCS)
Low Temperature °C
Pumping Viscosity
(mPa∙s) Max (MRV)
Viscosity (mm2/s) at 100°C Min Viscosity (mm2/s) at 100°C Max High Shear Rate
Viscosity (mPa∙s)
at 150°C Min
0W 6200 @ -35 60000 @ -40 3.8 - -
5W 6600 @ -30 60000 @ -35 3.8 - -
10W 7000 @ -25 60000 @ -30 4.1 - -
15W 7000 @ -20 60000 @ -25 5.6 - -
20W 9500 @ -15 60000 @ -20 5.6 - -
25W 13000 @ -10 60000 @ -15 9.3 - -
20 - - 5.6 9.3 2.6
30 - - 9.3 12.5 2.9
40 - - 12.5 16.3 2.9 (0W - 10W)
40 - - 12.5 16.3 3.7 (15W - 25W)
50 - - 16.3 21.9 3.7
60 - - 21.9 26.1 3.7

It is very important to understand that J300 SAE Standard defines the limits for a classification of engine lubricating oils in rheological terms only.
Other oil characteristics are not considered or included !


Now you might ask: "Why all that mambo jumbo and mass quantity of information?"

Based on our experience 99.8% of motorists have absolutely NO IDEA what the SAE Numbers on Motor Oil Labels really mean.

Many believe that the simple recommendations in their vehicle owner's manual are "cast" in concrete, and the SAE viscosity of recommended Motor Oil can not be changed under ANY circumstances.

The fact that it is quite appropriate to either increase or decrease the motor oil viscosity, which is recommended in your vehicle owner's manual.

If it is appropriate for YOUR particular operating conditions as well as desired engine life.

Here are some REAL time, as well as, laboratory tested "ultimate" and unchangeable truths:

  1. The ideal oil viscosity for motor oil used in conventional piston engine operating at the "normal" engine operating temperature is equivalent to SAE 30.

    (In range of 9 cSt to 12 cSt @ 100 °C)

  2. If you use thinner oil (SAE 20) under these "normal" operating conditions there will be LESS resistance to motion due to reduced viscosity, and therefore BETTER Fuel Economy will result.

    This gain in fuel economy does not however occur without costs:

  3. If you use thicker oil (SAE 40 or SAE 50) under these "normal" operating conditions there will be MORE resistance to motion due to increased viscosity, and therefore WORSE Fuel Economy will result. This LOSS in Fuel Economy is somewhat compensated for by:
  4. If the ambient or operating temperature is INCREASED from the "ideal" or "normal" (70 °F) then the oil viscosity MUST BE INCREASED to assure same level of protection and lubricating oil film integrity.
    (It is not just better, but a must to use SAE 40 oil at 100 °F ambient and SAE 50 at 120 °F ambient)
  5. If the load is increased such as when towing, the oil viscosity MUST be increased to assure the same level of protection. (Use SAE 50 when towing)
  6. If the engine speed is INCREASED such as during long distance high speed driving in low ambient temperatures (so that the bulk oil temperature is not increased) the oil viscosity could be DECREASED that is SAE 20 is preferred to SAE 30 oil. (This however works ONLY in manual transmission vehicles where vehicle speed and engine speed are proportional and higher RPM can be maintained by more frequent downshifts if necessary)
  7. If the load is decreased then the oil viscosity can be DECREASED
    (When Empty Tractor is driven at 70 MPH on Interstate, it is OK to use SAE 30 instead of the SAE 40 that is specified and appropriate when the Tractor is hauling maximum load at 55 MPH)
  8. The most important factor related to long-term engine durability and component wear seems to be:
    High-Temperature / High-Shear-Rate specification shown in the last column of the SAE J300 Standard.
    For SAE 20 oil it is 2.6cP minimum.
    For SAE 30 oil it is 2.9cP minimum.
    For SAE 40 oil there are two specifications 2.9 cP same as SAE 30 and 3.7 cP which is the same for SAE 50 and SAE 60, but why? Well the first specification is for light-duty engines (cars that are not expected to last beyond 70,000 to 150,000 miles) and the second for heavy duty engines (that is engines which are expected to last up to 1,000,000 miles). That is why oils which are labeled as HD or Heavy-duty must satisfy the second SAE 40 specification of 3.7 cP.

OK the final scoop on SAE 5W-20 and SAE 0W-20 oils:

You will definitely get better mileage with SAE 5W-20 then SAE 5W-30 oil, but not by much, usually the optimistic estimates are LESS than 3%.

In several separate and independent of each other studies published in SAE papers by Engineers working for GM, Honda and Toyota the improvement over SAE 5W-30 Motor Oil was with SAE 5W-20 Motor Oil in 1.5% range for their respective standard production engines.
It is also interesting to note that in all those studies and papers the engines were operated only for the equivalent "warranty" period, to determine that there was no detrimental effect on engine durability.

If you purchase the SAE Papers referenced below and take the time to read them, you will find that the longest tests performed were only 10,000 miles or 500 engine run hours!

The bad news is that in real life operation about 30% reduction in engine life is documented.

(From 100,000 miles or 10 years to 70,000 miles or 7 years).

Only manufacturers who have 3 years or 36,000 miles powertrain warranties currently recommend
SAE 5W-20 oil to be used in some of their NEW 2002 through 2013 model vehicles (FORD, HONDA).

By contrast Mercedes-Benz that offered 4 years or 50,000 miles warranty not only specified
SAE 5W-40 motor oil, but in the USA, to assure that only that oil grade was used, provided periodic maintenance FREE to all its customers.

(Free maintenance was offered by Mercedes-Benz from 2000 model years through 2004 model year, it was cancelled on 2005 model cars and SUV's)

ALL heavy-duty engine manufacturers recommend SAE 40, SAE 15W-40 or SAE 5W-40 oil.

However, there is a trend to "experiment" in Heavy-duty Engines with SAE 5W-30 Motor Oils to get "better fuel economy".

Currently, no OEM is daring to even mention the use of SAE 5W-20 in any of their Heavy-duty Engines.

Of course if there was "absolutely" no adverse effect on wear and engine durability, the Heavy-duty vehicle owners would be the first ones to embrace such lubricant !

Why ?

The reason is simple Heavy-duty trucks average about 7 miles per gallon, and travel 30,000 to 100,000 miles annually, at over $4.00 per US Gallon of Diesel Fuel the "pay back" would be in thousands of Dollars!

But HD vehicle owners and operators also know that typical engine overhaul costs from $16,000 to $32,000 and the money saved on fuel can be very quickly spent on premature engine rebuilt due to excessive wear.

FINAL choice is yours, you can get BETTER mileage, or LONGER engine life.

If you are leasing a vehicle, then the BETTER mileage parameter is definitely more important as well as cost effective. You just do not care how long will engine last on a car that you will only operate for 24,000 to 36,000 miles. But how many Gallons of fuel you will burn will make a difference.

If you own your vehicle for the long haul, or indefinitely, then SAE 5W-50 is absolute must!

That is why SynLube™ Lube‑4‑Life® is available ONLY in that grade, since we guarantee 150,000-mile service life from engines that were engineered to last not more than 100,000. It makes that much difference!

But due to unique colloidal technology used in SynLube™ Lube‑4‑Life® you still get mileage benefit that is 1.8% to 3% better than even SAE 5W-20 petroleum motor oils that are now used by some OEMs.

With SynLube™ Lube‑4‑Life® you DO NOT have to sacrifice engine life to get BETTER fuel economy! You get both: lower fuel consumption AND longer engine service life!


Now it would NOT be fair if we did not explain what is the incentive for FORD and HONDA and other manufacturers to promote and hype the SAE 5W-20 motor oil for use in their NEW vehicles.

For many years in the USA automotive manufacturers and importers have been subject to CAFE (Corporate Average Fuel Economy) Standards that were passed by US Congress during Fuel Shortages and fears of America running our of Gasoline in few decades. These laws when enacted forced US auto manufacturers to not even match the fuel economy of then popular Japanese Imports.

The CAFE standards were (and still are) 27.5 MPG for cars and 20.7 MPG for trucks. And they were unreasonable when average US made car got 12 MPG. But also reasonable when average Japanese car got 34 MPG. People bought cars or station wagons, mini vans and SUV's were not yet invented (or designed) and people used trucks for business and not commuting.

Today 52% of vehicles sold are in the "truck" category (SUV, Light Trucks, mini-vans) and most NEW vehicles get 8 MPG less than the "trade-in" vehicle they replace.

GEO METRO that got 50 MPG without any high tech tricks, because it is small light car, did not sell, there were over 2,500 units made year ago still on dealer lots throughout USA, after the production was discontinued in 2000 model year and majority of sales were not to private individuals but to rental fleets. At the same time there was 6 months waiting list for the latest SUV's that get only 12 MPG, like for example the very popular DODGE Durango.

Car manufacturer gets a hefty Federal Fines for not meeting the CAFE MPG standards for every 0.1 MPG by which they fail, multiplied by the number of vehicles they sell.

That is $5.50 per each 0.1 MPG by which the standard is missed multiplied by the number of vehicles sold in previous model year.

Ouch, that runs annually into millions of dollars.

The success in the car industry is measured ONLY by how many vehicles have been sold in last 10 days.

Customer satisfaction, customer loyalty and especially vehicle durability, as long as it survives the initial warranty period is ABSOLUTELY of no concern.

Therefore every 0.1 MPG by which you can rise fuel economy does matter, and manufacturers are quite willing to sacrifice engine durability, after all the sooner you will wear out your new car the sooner you will buy another and that is positive impact on the 10 day sales statistics.

Nothing else really matters, not now, not latter.

SAE 5W-20 Motor Oil is GREAT - It yields better EPA numbers than SAE 5W-30 oil = better CAFE = lower Federal Fines for not meeting minimal CAFE standards. It typically to the manufacturer saves about $15.00 per vehicle in Federal CAFE Fines.

SAE 5W-20 Motor Oil increases oil consumption - More oil gets used, just great for oil companies everywhere.

SAE 5W-20 Motor Oil increases mechanical wear, reduces engine life - that way you will buy new car sooner = more sales for car manufacturer.

Everybody wins, but the vehicle owner, who has to pay more per mile driven in the long run.


If you though all of the above is a "bad news" then brace yourself !

The EPA issued new fuel-efficiency standard; Autos must achieve CAFE of 54.5 MPG by 2025.

American-made cars and light trucks will have to average 34.5 MPG by 2016.

As a result there is already talk of "new" SAE Motor Oil specification and that is introduction of SAE 16 Grade, a viscosity, which is even "lower" than SAE 20.

WOW !!! - more on that one in one of our future web pages........

Latest Development

For 2015 Model Year top of the line Chevrolet Corvette Z06, General Motors not only does not use SAE 5W-20 Motor Oil as a Factory Fill, but recommends the use of Synthetic SAE 5W-30 Motor Oil as a Service Fill.

In addition, for on-track and high-performance applications, Chevrolet is recommending that owners use SAE 15W-50 Motor Oil to ensure "full engine protection and optimal engine efficiency".


The use or fuel-efficient oils provides modest benefits to fuel economy at very low cost to the consumer.

The SAE 5W-30 oil can be used in most 1991 and later vehicles, and can provide a fuel economy benefit of one to two Percent relative to SAE 10W-30 Motor Oils, and even more at cold ambient conditions.

SAE 5W-20 Motor Oil can provide an additional 1.5 percent benefit in fuel economy relative to SAE 5W-30 Motor Oil and can be used on a large number of post-2000 models as well as several 1996 to 2000 models.

Many manufacturers have by now provided service bulletins to their dealers on the 1996-2000 engines compatible with SAE 5W-20 Motor Oils.

In general, caution should be exercised with the use of SAE 5W-20 Motor Oils in high performance vehicles, vehicles subjected to heavy loads or vehicles operated in very hot weather.

Various brands of both (SAE 0W-20 and SAE 5W-20) of these "low viscosity" oils are available in retail outlets and cost differences between oils of different viscosity range from zero to $2.90 per quart, depending on brand.


When to use SAE 5W-20 (or SAE 0W-20) Motor Oil ?

When NOT to use SAE 5W-20 Motor Oil

Want the BEST of both Worlds ?

If you want the best possible "fuel economy" and also minimized Engine Wear, consider the use of better oil like: SynLube™ Lube‑4‑Life® SAE 5W-50 in you vehicle.

The CHOICE IS ultimately YOURS !


Want a second opinion, here is link to an excellent article from Noria about the "Wear v. Viscosity".

SAE Papers

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