Originally Posted by 91Cherokee7
I have been using STP oil filters but i may switch to NAPA GOLD.............. Engine oil pressure when cold is 32 (ish) When hot 40 to 45.
Usually....cold oil pressure is higher
than hot oil pressure. That is odd.
What weight oil do you use? I use 10W-30 Mobile 1 Full Synthetic oil. I change it every 6,000 miles. I also use a Napa filter. The one for the 4.0 is a Napa 21085.... BUT..... I use a Napa 21515 which is actually a Ford 5.0 filter which has ~35% more filter volume. Has the same threads and diameter but is ~1 1/2" longer.
Oil pressure is not as important as oil flow. Oil pressure is a measurement of resistance
All oils thin to 10 weight when the engine is at operating temperature with some exceptions.
How does the oil flow when it is cold is most important. Even at air temperatures of 75F, cold regular oil is as thick as molasses.
Years ago a trick was done to clean up an engine oil system and remove small engine 'noises' like sticky lifters. This can be dangerous if not done properly.
One would add a quart of kerosene to the base pan oil. Then the engine would get fired up and left running AT IDLE for four or five minutes. LISTEN very carefully. Any increase in engine noises means shut it off. The biggest clogger in an engines is detergent mixed with oil/crud particulates. This basically is an engine 'physic'. Shut of engine wait for an hour and drain well and let it drain until nothing is coming out. Fill it with clean oil and a filter and see what that does for noises.
Spec this out;