Hi-

I have a 2001 Jeep Cherokee Sport (4x2, 4.0 liter engine).

My oil pressure typically reads around 30 when on and idle and about 45 when under highway loads (the gauge goes from 0 to 80 with 40 as a midpoint). I took it out for a short drive this morning and it was idling at 40 and pushing up to around 60 when under a load... and hit as high as 65.

I took it home and shut it off in the driveway for a few minutes and then started it back up. The oil pressure gauge continued to read 40 when idle, but only hit 60 when I hit the gas and took the RPMs up to 3500.

The vehicle has been well-maintained, with oil changes every 3500 miles or so. It has 116,000 miles on it and has not seen harsh driving conditions (I live in San Antonio, Texas).

EDIT: Last oil change was approximately two weeks ago... done at one of those "Express Lube" type places... I've been going to this place for many years without issue.

Any ideas on what could be causing the oil pressure to spike?

I have a 94 Jeep GC 6 cylinder 4WD with 176K on it. The oil temp at idle is usually around 40 and around 60 to 65 highway. Your oil sending device is just getting old and now is properly sending the right pressure readings. My car has always had those pressure readings from day one.

I recently had a transmission fluid exchange and my oil pressure readings are down a tad to 38 or 35 idle and 58 to 60 highway.

When did you change your tranny fluid last?

I was thinking the same thing as I drove home from work this evening.

I think it may finally be giving the right reading. It runs as high as 70-80 when cold... and then, when warmed up, idles at 35-40 and only gets up to 60. The transmission fluid... I've never had it changed.

Yes, when I first start in the AM the pressure reads higher as well until everything gets warmed up.

By all means have the fluid in the tranny changed out. I saw much better performance and smoother shifting into overdrive the first few days. You don't want to leave the old fluid in if you have over 100K miles and not have it changed. Actually, they say that you should change fluid every 30K miles. You can judge the fluid's color if you are there and see it changed out for the fresh fluid. My old fluid was still red but not the bright red of new fluid. Every 3 fluid changes should have a tranny fluid screen change as well. If you don't see the improved shifting, get the screen changed asap so you get the dirt out of the fluid. I go to one of the quick lube places and watch what they do. It only takes about 30 minutes tops and costs less than $100 there to change out the tranny fluid. You'll get a bit better gas mileage also. Our cars take about 18 quarts of fluid since the tranny is so big.

I am also using the Valvoline high mileage oil when I get oil changes. Costs a bit more but I feel it's worth it.