Bud said: I'll bet that no Honda engineer would ever use such a viscosity. It makes absolutely no sense at all other than to give companies the opportunity to claim a few tenths better EPA mileage to keep them from having to pay gas guzzler tax.
I would disagree completely. I am confident that Honda, Mercedes, Ford engineers all are very happy to be a part of a decade of engine development that sees better bearings, pistons, rings, cylinder bores, manufacturing techniques, etc. that allows them to use oils that have tremendous film strengths and result in lower internal friction and better performance from the engines they design.
I can not think of one race team that I was ever involved with that ran any oil thicker than 0-30wt or 5-30wt. And in many cases for qualifing oils of viscosity as low as 5 and 10wt.
High viscosity oils (40wt and 50wt), given todays better oils and engine parts are a thing of the past or an indication of poor engineering skills.