CAFE Standards in the US and Oil Grades

Why can a SAE40 be used hotter than a 15w40?
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Wasn't it you who just cut off the usual arrows?
 
"Accommodating" for thicker or thinner oil could be as simple as larger or smaller holes in internal engine parts. I can see there being a difference in that. Somebody look up parts for a US and UK engine that facilitate oil flow and see if there's a difference.
 
"Accommodating" for thicker or thinner oil could be as simple as larger or smaller holes in internal engine parts. I can see there being a difference in that. Somebody look up parts for a US and UK engine that facilitate oil flow and see if there's a difference.

The Ford 5.0L Coyote engine literally spec'd 5w-20 or 5w-50 depending on whether you got the "track pack" version of the car or not, which included different ECM programming (higher thermal castration temperature threshold) and an oil cooler.

Engines are simply not that sensitive to viscosity, they can't be, given the relationship it has with temperature.
 
Exactly. A 5W-30 in Miami will be significantly thinner on start-up than a 0W-20 in Minneapolis in the dead of winter. And once at operating temps and above, the viscosity spread lessens.
 
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I'm guessing maybe the mono grade (SAE40) is "tougher" per se than the multi grade and can take more of a beating under hot conditions.

In other words, a straight SAE40 probably has a higher HTHS viscosity due to lack of VIIs. It's really HTHS viscosity that matters.
 
Why can a SAE40 be used hotter than a 15w40?
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All things equal the straight 40 oil is thicker between the parts. Look as well at the 30wts [conventional]
 
40 celsius is 104 fahrenheit, 45 is 113. So are you really worried about this difference? It is just manufacturers best effort advice. If you are driving when it's over 104 change it to straight 40. When it is above 113 then must stop driving and pull over. The cooling system keeps the engine to 225 or whatever, it isn't going to be a problem.

Besides CAFE manufacturers have to compete with each other. If Toyota can beat Hyundai by one mpg, there are a lot of people who will go for the higher number even if it means nothing.
 
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40 celsius is 104 fahrenheit, 45 is 113. So are you really worried about this difference? It is just manufacturers best effort advice. If you are driving when it's over 104 change it to straight 40. When it is above 113 then must stop driving and pull over. The cooling system keeps the engine to 225 or whatever, it isn't going to be a problem.

Besides CAFE manufacturers have to compete with each other. If Toyota can beat Hyundai by one mpg, there are a lot of people who will go for the higher number even if it means nothing.
If it were no diff then why would they just not make them the same on hi end?
 
Oh? So a 40 is ok to use where a 60 should be used when the temps are that hot?
I thought they had limits.

Why can a SAE40 be used hotter than a 15w40?
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That chart doesn't appear to be from any owner's manual for a specific piece of equipment but rather comes from this article:

Actual owner's manual examples would be like this one from CAT for the 3500B/C engines:
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Which shows 5w-40/10w-40/15w-40 all suitable for the same upper range of anticipated ambient temperatures.

And an E39 BMW manual, shows synthetic (BMW) 5w-30 good for all temperatures, 15w-40 if using conventional for above -10C and conventional 5w-30 for below 10C:
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That chart doesn't appear to be from any owner's manual for a specific piece of equipment but rather comes from this article:
You find that chart? On one website? And you claim it come from one article? Now that's funny.

I found it on another site, and it can be found on 10,000+ other websites out there, it's a generic SAE oil-temp chart, etc.

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You find that chart? On one website? And you claim it come from one article? Now that's funny.

I found it on another site, and it can be found on 10,000+ other websites out there, it's a generic SAE oil-temp chart, etc.

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I opened the link to the image you used, which took me to that site. So yes, it quite literally, when you posted it, came from that article. Are you being intentionally daft or just don't bother to actually look at the sources from which you pull?

I really do like how you came up with some random number to support whatever point it is you think you are making though, and bravo for not addressing any of the material I posted, your trolling game is really on-point today. (y)
 
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My guess is that you could use 5W-30 in practically 90% of passenger cars in the US. So why is there such an attitude of "USE WHATS IN YOUR OWNER'S MANUAL, OR ELSE!!!" and why is the language so strong in the US manuals?
Because of warranty requirements. Sure most passenger vehicle engines would run fine on 5w30. But if you use something not approved by the manufacturer, the warranty could be voided and claims denied. I think that is good reason for strong language and EMPHASIS.
 
Because of warranty requirements. Sure most passenger vehicle engines would run fine on 5w30. But if you use something not approved by the manufacturer, the warranty could be voided and claims denied. I think that is good reason for strong language and EMPHASIS.

The owner's manuals "recommend", they don't "demand" that a specific oil viscosity is used. And I've never seen any owner's manual statement that says warranty would be denied if a different oil viscosity besides what was "recommended" was used.
 
The owner's manuals "recommend", they don't "demand" that a specific oil viscosity is used. And I've never seen any owner's manual statement that says warranty would be denied if a different oil viscosity besides what was "recommended" was used.
VW tries their best to convince you of that as we discussed in another thread, but of course they end up saying that warranty will be denied if the oil you used caused the failure. No 504 00 oil in this application will cause engine failure, plain and simple. If anything it will help to prevent one.
 
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