Quote:
Originally Posted by Formulajones
That's what I also found by accident with a flat tappet cam I ran, using the same viscosity, that I mentioned earlier. I'm not sure of the reason other than the additive packages vary among manufactures, not the zinc specifically but the additive package as a whole.
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Part of that is the oil weight ratings are a mile wide. Some 10W30s thin out to almost 20 wt, and others are closer to 40wt when they get hot. So if you change oils and the actual viscosity is different, I would expect changes in lifter noise and some small change in hot oil pressure.