10W40 too light?

famous bob said

Have any of u guys read studies on hot engine oil? there was about no diff. in thickness between 50 wt. and 20wt. at 200 or more degrees , it all thins considerably when hot , on conventional style oil, "from bill Jenkins book." About the newer oils ????????????

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Mattax is right on about this. There's still a difference, and it can be important.

But more importantly, it doesn't matter in this case

@Dave NEO 's engine is pushing 30 psi even when hot. His engine shouldn't be making any noise because of that pressure, it's high enough.

So the problem likely isn't which oil he's running or what viscosity it is, he should be looking for what/why it's making noise. Maybe the top end of the engine isn't oiling properly, or the valvetrain is out of spec, or the lifters are going bad, or the cam is going flat, etc.