Need advice on oil pressure

97 4.0L Auto 4x4 on 33s stock gears 220,000 miles. I am very good about maintenance and oil changes been running synthetic oil (10W-30) and synthetic Lucas oil stabilizer for atleast 100,000 miles and before that I ran a synthetic blend and conventional Lucas oil stabilizer. I used to change the oil every 3,000 miles but in the past year I have extended that to 5,000-6,000 miles to save money and since I run full synthetic I felt I was ok doing this. After I did my last oil change the other day I noticed at startup and driving it was running at 51 psi under load and woul fall to 47 if just cruising. As it warmed up it would bounce between 45 and 47 cruising. At a stop but still in drive once warmed up it would sit at 40 but after a while of driving it would drop as low as 28 at a stop or in park. Does this all sound normal for a Jeep of 230,000 miles? Never really paid too much attention to pressure since it has always seemed to be around 40.

that actually seems pretty high. Does your jeep take 6 quarts to fill? is all the lucas coming back out?

FSM specifications are not less than 13 psi at hot idle, and between 37-75 psi over 1600 rpms.


If you think the gauge reading are incorrect, clean and inspect the pressure sender plug and wires, and consider buying a new sender.

Your numbers are absolutely fine. Enjoy your XJ.

birchlakeXJ said:

Your numbers are absolutely fine. Enjoy your XJ.

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Ok good seems like I am from the specs that Tim_MN posted so I'm not gonna worry about it. My XJ runs great considering the age and mileage and when I replaced the RMS and valve cover gasket there is literally not an ounce of sludge in my motor.

Don't bother with the Lucas Oil Stabilizer. Doesn't do anything. Your OP sounds kind of high to me as well. Not bad though by any means.