Originally Posted By: Shannow
Originally Posted By: Cujet
Originally Posted By: JHZR2
People speculate that it is CAFE, [the requirement for thin oils]
It's not speculation, Ford engineers and other manufacturers came right out and said so.
It seems to be a manhood thing that the OEMs going [for thin oils] for CAFE purposes is emasculation.
Which leads to the "improved flow", "better cooling", and the infamous "dragging rated towing capacity through death valley in Summer".
Which I've not seen a Ford Power Train engineer come on the site and provide statement/evidence of as yet.
Hogwash. Emasculation? Where do you come up with this stuff?!?
By such logic none of the gains in power output, longevity, etc would have ever come about save for CAFE, which is a loose way of saying "Government".
You of all people should understand that as asperities are reduced, film thickness requirements also reduce.
So should our logic be that all manufacturing, machining, and design processes were good enough at late 1960s levels? They never would have improved but for government forcing CAA and CAFE?
To say CAFE is the only driver behind thin oils and the benefits they can offer is uninformed. Again, if there is copious data proving reduced longevity due to thinner oils, do share.
But many of the enablers that allow thin oils to be run, and higher power and economy to be realized are not solely the cause of CAFE. If they were, and manufacturers were truly scared of it, engines would be downsizing, power levels would be reducing, all the tricks to optimize SFC would be in play. Not just a marginally thinner oil that gives a fraction of an MPG benefit if that.
Do thinnner oils reduce heat generation and losses in bearings? Is that a bad thing? Can other benefits be had?
If detailed analysis that is now available shows that a certain vehicle design allows for a certain bulk oil temperature, and a certain bearing oil temperature, viscosity and film thickness is appropriate to the design, is there a good reason to push excessively more "engineering reserve"?
Let's take my 135i as a good example. It runs 245F bulk oil temperatures in routine use. A good deal hotter than what Ive observed in most other vehicles. BMW only specifies LL-01. Common sense would suggest that for this engine, the necessary viscosity and HTHS, as mere objectively testible parameters should likely be higher than for a more pedestrian engine with possibly greater cooling capability and reduced power compared to my 135i. So I'd readily run a 0 or 5w-30 LL-01 oil in a 128i, while 5w-40 is certainly a reasonable option for the 135i.
So back to my OP... a crate engine, with no control into frontal area, oil cooler and radiator design, use profiles, etc would be reasonable to spec the most conservative choice.
Doesn't mean that it's necessary by design, especially if/when other critical interfaces are well designed /engineered to assure certain conditions are met. To say that the coyote engine couldn't last the same long life with 20wt that it would with 30, 40, or 50, without objective data and strong basis, is indeed speculative.