Originally Posted by Heitmann

Hi

I have for some time been driving with a K&N oil filter on my car
and did notice when engine hot (+80 degrees) and idling I would se lower oil pressure than the 26 psi stated in the manual.

So I have changed back to a standard Motorcraft oil filter and my oil pressure is back at where is should be on idle.

It seems that the K&N oil filter made me loose about 5 psi on idle - I did not notice any significant drop at higher rpm (but didn't look for it either).

If I hadn't experienced this myself, I would not beleive it (I have tried 2 different K&N filters and I am running on Silkolene Pro S 10w/50)

But what can cause this kind of drop, just by changing filter?
One theory is that the K&N has better flow, and therefore less restriction=less pressure. but don't know if this is how it works

any view on this ?