My 98 XJ's oil pressure sits at about 10 when I'm at idle and when I accelerate it goes up to 40, and when I cruise at a constant speed it stays at about 35-40. I'm not sure If the oil pressure should drop that low while I'm at idle.

 

I think lower spec at hot idle is no lower than 12 or 13 psi. Should run between 40 and 60 while driving.

 

Mines sits at 40 till I go then up to 60

 

A shop can test/verify oil pressure with a known accurate test gauge. Good oil pressure is 10 psi/1000 rpm....much over that (if it's actual) just wastes power.

 

I mean it doesn't run rough or anything, and performs great, I just wasn't sure 10 psi at hot idle was too low. But it apparently isn't too far from spec.

 

Stock gauges are not the most accurate either, almost like an on/off switch. ITs better be safe then sorry.

 

Never hurts to verify the accuracy of a factory gauge as they are known to be inaccurate.

 

correct.

 

1. Get a hold of a "MECHANICAL" oil pressure gauge. Can be rented from many parts stores, call around. Only a few bucks to rent.

2. Remove the oil pressure sending unit and install the mechanical gauge using the correct adapter.

3. Compare your readings with the mechanical gauge to what you are seeing on your gauge. Then you will know for sure.

4. Below are the oil pressure specs for the 4.0. Yes, 13 psi is the low spec at HOT idle, but I have seen many 4.0 engines last a long time with 10 psi.

*Not less than 13 psi at HOT idle
*Between 37-75 psi over 1600 rpms

 

Thanks for the info, looks like I'm ok.