[PeteKz]

I have spent years reading up on oil formulations and tests, and I think I know less about motor oil now than I did 20 years ago, and I'm a mechanical engineer! But I've come the conclusion that almost no one knows as much about oil as they think they do--including the engineers who formulate it. Why? Because they are always operating under constraints of time and cost.

One thing I do know with certainty is that the manufacturers regularly change their formulations, not just to meet newer specs, but also to cut costs. Thus, what you bought last year may not be the same product in the same graphics bottle as this year. Another conclusion I've reached is that the total oil formulation is more important than the amount of zinc/phosphate in the oil. Yes, even for solid cam/follower engines. The amount of zinc or phosphorus is a proxy for the ultimate lubricity of the oil, but not a direct measure of it, and newest SP formulations with moly and titanium additives don't need as much ZDDP. So don't think that is the most important measure. I've made that mistake too.

That said, the web site that I think provides the best brand-to-brand testing info on motor oils is run by a guy that goes by "540 Rat". He's an ME too, but pretty evangelical in his writing style, which always turns me off, but I can't find any better info. Certainly not at the oil manufacturers sites, which appear to be designed to provide the minimum info approved by their marketing departments.

Anyway, read the information for yourself. https://540ratblog.wordpress.com/