5w-20 motor oil : who's using it ? ...

[SilverGlow]

Originally Posted by TheSilkySmooth

This is an oversimplification on your part. The oil must provide adequate viscosity for the running clearance of the engine design - most critical are the journal clearance and piston to wall clearance. If you run an inadequate viscosity you will easily have catastrophic engine failure. As for margin lube contact wear in cam lobe-to-tappet face, piston top-to- bore, crank flange to journal thrust cap, and unfortunately add for our engines; timing chain sprocket to guide and chain to sprocket. Proper lubrication here relies all on the polar nature of the base oil (most popular syn are NOT polar) and the metal salt extreme pressure additives in the oil. Without them you WILL have premature wear no matter how good your base oil is (Good as in Motul, Redline, Fuchs, ELF NOT Mobil, Pennzoil, BP!) If toyota specs 30w and 20W they are really flirting with disaster. The motor MUST be clearanced for one or the other. Guaranteed we will see a high percentage of spun bearings and collapsed piston skirts with this misguided TSB policy on our 1nzfe engine.

Sonja's Dad

But your write up does not apply to this discussion.

You know why?

You are the one that is over-simplifying this issue. Why then do many UOA reports (Used Oil Analysis) show that using 20 weight oil does not in fact show more wear and tear?

Because Toyota has back-spec'd our cars for 20 weight oil, and if it would cause engine failure, then why would they invite millions of in-warranty repairs by publising the TSB, which states we all can use 20 weight in our cars.

And you know more then Toyota engineers? Why would Toyota willfully dirty their reputation and name by telling us to use 20 weight oil if it will cause enginen damage? Please.....

The only way what that what you write is true is if someone uses 20 weight on a engine THAT IS NOT SPEC'D FOR 20w oil.

This is not the case with our Yaris 1.5L engines.