Oil Pressure normal (40) cold drops when Warm (20)

[GregGA]

4.0 isn't fussy about motor oil or oil pressure. 10 psi at idle and 40 at higher rpm's is enough for long term reliability.
If you drive foot to the floor bouncing off 5000 rpm then a little more oil pressure at speed is nice..

Yep, we could run our engines on Wesson oil. But some of us are a little bit
wacky, and appreciate the heritage of the engine and the Jeep. I could feed my Jeep Big Lot's oil and Fram OCOD. But that is just unAmerican:sad1:

Here's to those who care enough to go out an buy a mechanical oil pressure gauge:yelclap: and try to learn the effects of different oil/filter combinations on their engines!