Originally Posted By: OVERKILL
Originally Posted By: turtlevette
Any study, paper or theory can be cut up. There's nothing out there that proves running a heavy oil in a passenger car is the way to go either.
The preponderance of evidence supports the lighter oil philosophy.
What about the "use what the manufacturer suggests based on the details in the owners manual because they tested the engine" philosophy?
Whoa, I know, let's not get too logical here
Seriously though, if the OEM calls for 5w-20 in Texas or Antarctica you are fine using it in either. If they call for a Euro oil with an HTHS >=3.5cP for those conditions, then use one. In the latter situation, I'd prefer an oil with a higher VI/better visc spread (ala 0w-30 or 0w-40) but there is probably no measurable impact on the overall life/health of the engine.
If the OEM gives you a range of viscs based on temperature, you are safe to follow it.
As Shannow has noted in the past, engine design (bearing surface area for example) has changed to accommodate the overall trend toward thinner oils. That does not however mean that you should run 0w-20 TGMO in an M3 that spec's 10w-60. If BMW wanted you to run 0w-20 they would have spec'd it. On the other hand, if you have a Ford 5.0L that spec's 5w-20, you aren't going to damage it by running 5w-50 in it. After all, Ford also spec's that grade for that engine. Of course that doesn't mean it is necessarily the best choice for it either if it never sees a race track. And running 20w-50 in something that spec's 5w-20 in Alaska in February would align with the M3 example in being ridiculous and could, like with the M3 example, result in significant engine damage.
Thin oils, as Doug Hillary has mentioned in the past, are not something new. SAE20, 20W, 20W-20 have been around for a very, VERY long time. An engine's ability to heat and stress the oil correlates with its viscosity requirements. Low power density engines don't have the ability to heat the oil the same as a high output one and subsequently don't require the same buffer. And while oil temperature can generally be addressed with sump size and oil coolers, HTHS viscosity is still an important component and in high stress applications, even if you are able to keep bulk sump temps down, you may still need an overall heavier oil to deal with the high stress/high heat spots in the engine.
We have all the data we need in front of us: the recommendations and requirements of the manufacturers. If they tell you thin, then use thin. If they tell you thick, use thick. This subject need not be so polarized.
I agree with you. The oem's aren't going to recommend a lubricant that's going to lessen the useful life of their products. That's bad for business.
However I do believe that a person needs to consider their particular usage and decide accordingly.
For example my 4v in my mustang. I didn't have a real oil pressure and oil temp gauge on it last year. This year they're already installed,as well as a big oil cooler.
I want to see what my max oil temps when I'm driving hard. I've got no doubt that a 20 grade is adequate,especially if oil temps never exceed 220f however if I find that I'm getting 260f and staying there then I'm going to run your baby ,M1 0w-40 in it because I know its stellar at temps that high and higher.
My charger,same thing. In the winter running a 40 grade is retarded since oil temps rarely exceed 220f in day to day operation however in the summer I drive it much harder and oil temps are going to be much higher and that should be considered when making an oil grade choice.
On a vehicle that's driven normally,that never exceeds its designed limits there is no reason to go any thicker than the oem prescribes however if the engine is going to be operated in a more "spirited" manner then that should be taken into consideration as well.
Just arbitrarily going thinner without data is retarded. No engine ever wore out/was damaged from using an oil that a grade thicker than prescribed but thinner is a risk. No matter what a fool believes.
