Originally Posted By: Shannow
If you have a pressure gauge, it reaches a figure then stays pegged. You can rev it cold, and see where it tops out at.
No you can't (not on all cars). From what I've observed, the bypass restriction is going to let the pressure go higher when the oil is cold and thick and in full bypass mode. When the oil is hot and the pump is in bypass mode, the oil can pass through the restriction easier, and you see the true bypass value determined by the calibrated bypass valve spring .
I see my pressure bump close to 60 psi on the gage in my other vehicle when cold. When hot, you can rev it until it blows, and that gage will never to 45 psi.
I don't know how many millions of Chevy V8s ever survived the 1960s with no overdrive, running down the highway at 3000 rpm with pumps at the full 45 psi bypass for 1000s of miles with SF or lower API oils?
You guys are making too much of this bypass deal. Pumps run in bypass in all engines. It is not going to overheat your oil if you run the pump in bypass mode at high revs, unless we are talking about a track car. Can't see it ever being a concern on the street.
So anyway - back to the question at hand... Assuming I don't care about running a thicker oil than required, are there any real negatives to using M1 0W-40? From what I see, it's a superior oil to 5W-30 at the same price? Am I right, or am I missing something?