Quote:
Originally Posted by ConnClark
...Also most engines have a bypass valve that allows the oil to bypass the filter once the pressure across the filter reaches a certain limit....
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My guess would also be that the resistance of the filter element is rather puny compared to the total resistance of oil flow.
But, just the fact that there is a bypass, in case the filter is plugged, or I would also assume in case it's 'just too cold', shows that the filter can offer a real resistance to oil flow.
I notice that my oil pressure is always up around 80 psi when I start, regardless of RPM, and gradually reduces to 40 or so once it is fully warmed up (1/2 hr. driving time). But since it is at 80 psi no matter the RPM I have always assumed it is likely flowing the oil thru the bypass, at least when above idle speed. This is true even when using 0W-30 Mobil-1.
It must take some HP to push that oil but like you say, the filter itself is probably a very small amount of the total oil flow resistance.