problem which is worrying me some when car is idling the oil pressure sits around 10-20 but when I'm on the gas even cruising with touch the gas peddle it sits perfectly at 40 put as soon as i release gas peddle it goes back down to around 10-20 again hopefully can figure out what the problem is soon as don't want to drive it with it fluctuating like that. any ideas where to start looking would be helpful as new to the jeep world.

 

that is fine do you have a mechanical gauge or just the oem one? you can buy a mechanical or rent one but that is the only way to be sure of an accurate reading

The oil pressure spec for the 4.0 is as follows:

*Not less than 13 psi at HOT idle

*Between 37-75 psi over 1600 rpms

mine sits at the first mark at idle believe that's like 15ish psi and around 50 above idle.

 

its still oem one at the moment as just got it. just never saw one fluctuate before.

 

yeah the 4.0 fluctuate a lot more than most other engines. as long as you are at or around that firs mark at idle you are fine.

 

^^This^^
Also what brand of oil filter do you have on it? If it's Fram get rid of it and put a good quality filter Such as Mopar, Wix. I know when I changed out the fram filter my oil pressure went from 10psi up to 20psi at idle and from 30psi to 43psi while driving. But like ochp said first thing to do is verify you pressure with a mechanical pressure gauge.

 

Your good so stop worrying. Oil pressure is not a condition, it is the result of a condition.