SAE Paper on Engine Wear with 20 wt. oil

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I don't see how anybody can deny that thicker is better based on these manuals. We see 20 weights being defended often as "well the manufacturer knows best", but that's really not the whole story, because the manufacturer recommends 30 weight when they don't have their hands tied to maximize fuel economy tests for every last percentage point.

To me, that says the manufacturer doesn't recommend 20 weight, but the hoops they have to jump through do. Without CAFE tests, it seems we'd be steered into running 30 weights like elsewhere in the world, and like thinner oils are a calculated decision to reduce engine wear by "enough" but not as well as possible.


Based on opinion and emotion.
 
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I don't see how anybody can deny that thicker is better based on these manuals. We see 20 weights being defended often as "well the manufacturer knows best", but that's really not the whole story, because the manufacturer recommends 30 weight when they don't have their hands tied to maximize fuel economy tests for every last percentage point.

To me, that says the manufacturer doesn't recommend 20 weight, but the hoops they have to jump through do. Without CAFE tests, it seems we'd be steered into running 30 weights like elsewhere in the world, and like thinner oils are a calculated decision to reduce engine wear by "enough" but not as well as possible.
I think Your oversimplifying it.

Lower viscosity oils flow better. Modern engines like my Toyota 2.5l have a variable discharge oil pump where that might come into play - I don't really know. Obviously it can handle it per the Australia manual, and obviously the pump can move oil with a viscosity of 100+ when cold up to like 8 when warm.

Not to mention SAE grades meet at the edges - ie a "thin" 30 can be virtually the same as a "thick" 20 -, and 16 and 20 overlap if I am reading the SAE chart right. Of course oils shear, so there is that part of the equation.

I don't think you can make that blanket statement. Better at what?
 
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I think Your oversimplifying it.

Lower viscosity oils flow better. Modern engines like my Toyota 2.5l have a variable discharge oil pump where that might come into play - I don't really know. Obviously it can handle it per the Australia manual, and obviously the pump can move oil with a viscosity of 100+ when cold up to like 8 when warm.

Not to mention SAE grades meet at the edges - ie a "thin" 30 can be virtually the same as a "thick" 20 -, and 16 and 20 overlap if I am reading the SAE chart right. Of course oils shear, so there is that part of the equation.

I don't think you can make that blanket statement. Better at what?
Better MOFT.

This whole thing about better flow being more beneficial is bunk information. MOFT is how lubrication protects parts. If low viscosity flow is king for protection against wear, then why haven't we been running straight 0 weight oil for the past twenty years? Because we need thicker MOFT than that to prevent contact and wear between moving parts, not just flow.
 
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Better MOFT.

This whole thing about better flow being more beneficial is bunk information. MOFT is how lubrication protects parts. If low viscosity flow is king for protection against wear, then why haven't we been running straight 0 weight oil for the past twenty years? Because we need thicker MOFT than that to prevent contact and wear between moving parts, not just flow.
Then we should all run SAE 50 in everything?
 
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If there were no opinion or emotion at play on this forum, then there would be no forum, because we would all just be buying by-the-spec Supertech and be done with it.


Your comment was about the grade, not about brands. Todays modern oils are far better in every way. You can run a 20 grade or a 16 grade with no worries.
 
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Your comment was about the grade, not about brands. Todays modern oils are far better in every way. You can run a 20 grade or a 16 grade with no worries.
This is far too much of a blanket statement. While commuting on the freeway at the speed limit? Sure. In track use or heavy towing? No, you can't.
 
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Before the switch to 20 wt oil there was a paper (pretty sure by SAE) that described shorter engine life of 20 wt as compared to 30 wt oil.

As I call the requirement was that the engine would last 200K miles. I recall that number got reduced to 150K miles. Wish I could resurect that information. It was around 2010.
You should be able to search that paper on the API website if it exists.
 
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This is far too much of a blanket statement. While commuting on the freeway at the speed limit? Sure. In track use or heavy towing? No, you can't.


There are members here doing exactly that. Towing heavy loads over mountain passes.


A reminder, the W does not stand for weight.
 
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What if…. We use whatever the hell oil weight, brand, and service intervals we like? But then, there would be no need for a debate on BITOG. I’ve always appreciated the observations of folks that make their living in the automotive service industry.

To those folks, are we seeing oil related engine failures due to oil weights and brands or; are the majority of engine failures due to inherent engine characteristics and just plain neglect?
 
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But what if you are driving a vehicle that was built prior to these "improvements" ?? Like 1998 that was "backspeced " too 5w20?
Then stick with 5W30. That's what I did after briefly buying into the back spec hype when I had a Vulcan powered Aerostar.
 
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The original post made me chuckle. I saw this important thing once that made a big claim, no idea where it is though...

I also saw a paper once that said 20w oils are actually potable water and we should all be afraid of them. Can't seem to find it now though.....
 
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Way back in early 2000's I had a Ford 4.6l V8 - and they back spec'd from 5w-30 to 5w-20 via a technical service bulleting. That was obviously not due to cafe, so anyone remember why they did so?

There has been all kinds of speculation here over the years I have found in old posts - from Cafe - which can't be true since Cafe has never been back dated - to Ford wants to kill your old car.

 
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This is what has convinced me to step up to 5W-30 from 20 weights too. If 20 weights are equal for protection, then why do non-CAFE countries get owners manuals that call for thicker oil for the same temps where US owners manuals call for exclusively 20 weights?
There can be a variety of reasons and none of which revolve around engine longevity. Not to mention that historically the US market has been the most important for automakers worldwide and 20w oils have been spec'd for over 20 years and these engines have been cooking along for well over 150 miles.
 
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The ONLY reason for the super thin oils is LABORATORY fuel mileage testing. It has nothing to do with better lubing the engine. EPA requires the oil used in the engines by the manufacturers for EPA fuel mileage testing to be the same as the grade spec'ed in the owners manual. If they can squeeze out a tenth of a mile per gallon more on "x" number of test runs(say 26.5 vs. 26.4 miles per gallon, the EPA lets them average up to claim 27 MPG). Absolutely meaningless in real world driving but means a LOT to automakers. My 2005 CRV "requires" 5W-20 says the owners manual yet the same engine in CRV's in other countries does not recommend such thin oil. Why not? My 2010 Scion XD owners manual says to use 0W-20 but the same vehicle in Europe, the Toyota Urban Cruiser's owners manual recommends 0W-20, 5W-20, 5W-30, 10W-30,15W-40 and 20W-50!
Oil is ridiculously expensive in Europe and in some places speeds over 100 mph are allowed. The economics and operational requirements aren't exactly comparable to the US. As for the fuel savings of using a lighter grade it's between 1-2 percent vs the immediately higher grade (20 vs 30, 30 vs 40). Of course oil weight is but one part of the holistic approach used by automakers to improve CAFE. Downsizing combined with turbocharging is another (less rotational mass), Using electric pumps (steering, coolant, oil?) also reduce parasitic draw.
 
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Way back in early 2000's I had a Ford 4.6l V8 - and they back spec'd from 5w-30 to 5w-20 via a technical service bulleting. That was obviously not due to cafe, so anyone remember why they did so?

There has been all kinds of speculation here over the years I have found in old posts - from Cafe - which can't be true since Cafe has never been back dated - to Ford wants to kill your old car.

Our Ford rep told us at the time it was due to camshaft galling in the head. The journals were/are just machined into the aluminum heads without any bearings/bushings. This was in support of our Crown Vic patrol units with the 4.6 V8.
 
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