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what causes the oil pressure to drop?

D

dieselenthusiast

NAXJA Forum User
Location
Zuni Mountains, New Mexico
Ever since I bought my XJ over a year ago, I noticed that the oil pressure sometimes drops down to 30 when I’m at idle. Cruising speeds and acceleration brings the oil pressure up to 50. What would cause the oil pressure to drop like this? I have a 2000 XJ.
 
Rule of thumb for oil pressure: 10 psi at hot idle, 10 psi per 1000 RPM.

FSM says 13 psi at idle.

Throw a mechanical gauge on it to confirm the pressure for peace of mind.
 
Thanks guys, I was a little worried…… I have coolant and gasoline that keep showing up in my UOA’s, so I’m a little paranoid.
 
Last edited:
As the others mentioned, rest easy.....your oil pressure is great.

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

If you're in these brackets, no worries.
 
Thanks birchlakeXJ........... Like Joe said, I might add a mechanical gauge one of these days, especially once I install the oil dual remote oil by-pass filter.
 
winterbeater said:
You do have a 2000. You probably know about the infamous 0331 head. Watch for coolant use and mayonnaise on the inside of the oil fill cap.
Click to expand...

Yeah, I know about the 0331. I did a hydrocarbon test, but nothing showed up. I’m more worried about the gasoline in my oil. I had enough gasoline in the oil that it was thinning the viscosity of the oil.
 
One last point about the OP...
I was worried as well, thinking I bought a lemon when idle pressure was 10 psi on the factory gauge. Switch from a FRAM to a MOPAR oil filter as suggested on here, and gained 6-8 psi (factory gauge) of OP. Have never seen the problem reoccur in the last 4+ years.
 
scottie_p said:
One last point about the OP...
I was worried as well, thinking I bought a lemon when idle pressure was 10 psi on the factory gauge. Switch from a FRAM to a MOPAR oil filter as suggested on here, and gained 6-8 psi (factory gauge) of OP. Have never seen the problem reoccur in the last 4+ years.
Click to expand...

Good point. Always stay away from the "orange cans of death".
 
LOL "Always stay away from the "orange cans of death".

Let's give it a NAXJA acronym!

OCD syndrome!:cheers:
 
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