Originally Posted By: ksJoe
... It is a technical service bulletin that has come out since then that says 5w20 is ok. 5w20 must be ok, but it is not what the was originally designed for, or it would have said that to begin with.
But you're all suggesting 5w20, so I guess I'll surrender to the peer pressure
Hold on, let's look at this for a moment -- and perhaps penetrate some of the insane fog that has descended over this oil choice question since Ford and Honda took the 20 wt plunge, almost TEN years ago now. First off, remember that designers of things that will be used by a wide range of people, in a wide range of circumstances, are designed with ranges in mind, not specific values, for virtually all variables. This would most certainly include motor oils for cars that will be driven by humans ranging from intellectuals to idiots, living in places as diverse as Anchorage AK and Miami FL. On top of that, SAE viscosities are defined in terms of ranges themselves, not specific viscosities. Beyond all this, even the engineers at the worst car company in the world (whatever that might be), are going to build wide "safe zones" around parameters such as oil vis just so an idiot in Anchorage who makes an oil choice more appropriate for Miami won't instantly destroy his engine.
Second (or fifth or whatever...), irrespective of whatever range they designed for, without doubt, each maker who is now spec-ing 20 wt oils in engines that previously called for a 30, must have done a testing program to ensure that the new spec was safe and sensible. I don't know this for fact, but think about it, it must be true. If not, the first guy who has an engine melt down on a newly spec-ed oil WILL win a massive law suit against the car maker, should there actually be a fight over the oil used. These guys all tested the stuff, and would not be recommending it if it was not provably safe for customer use.
I've been testing the 20 wt waters myself, finally, and though I don't have any UOA yet, I'm pleasantly surprised so far. My TCH sounds great and performs wonderfully on the two 20s I've had in it so far (M1 0w-20 and HDS 5w-20). Even at full throttle, the engine sounds great. The wife's 07 Avalon, back spec-ed for 20 wt is next on the list for a 20 wt experiment. Only big question for me now is what to do with all that green GC I still have on hand...
Next, don't forget that Ford and Honda have been on 20 wts for over eight years now. If this stuff wasn't going to work out, we'd have seen mass disaster by now. But we have not. Please, one of you 20-wt-haters, show me the secret junkyard full of cars that died early deaths because their owners used 20 wt oils and they proved too thin to protect.
Seriously, use the stuff and don't worry about it. Do a UOA to verify your own circumstances if you need full peace of mind.