OK so when I start my jeep (cold ish 70 degrees) my oil pressure goes up to about 75psi. When I drive 10 miles down the road at idle it's at 30psi when I'm at 2 thousand rpm is the only it's at 40 psi. I'm fearing the worst (worn rings). And advice? 203 thousand miles. I'm gonna do a oil change to synthetic in the next couple days. Could it be the sending unit.?

 

That is not bad by any means. The lowest its supposed to be at hot idle is 13 psi, and driving average is about 35. 30 at idle and 40 driving is perfectly fine.

 

Agree with Brandon up there ^^

Sounds like it's well within normal ranges. It definitely couldn't hurt to change to a better oil, though. Maybe try a high-mileage synthetic as a bit of insurance.

 

Thank you! Definitely cleared my mind.

 

Unless that gauge hits zero....drive! My 4.0 has 4 to 20 psi and has ran fine for the last 6 years.

 

X2. The FSM states the minimum pressure to be 13psi at hot idle and I believe it says +10psi for every 1k rpm.

75 psi on cold startup though..

 

If there is any question just do a quick check with a mechanical gauge:

As well if you are truly low on money don't bother wasting it on synthetic oil.

 

13psi just means that the mechanical condition of ENGINE is satisfactory. It can run a very long time with less than that. Oil pressure indicates bearing condition NOT lubricating condition. With worn bearings you have lower pressure but GREATER oil flow....and that is exactly what you need!

 

More specifically, the number in the FSM should be read as "the manufacturer warrants the performance of the engine as long as oil pressure is above 13 PSI, and should perform repairs if under".

75 PSI on cold start? What are you running in that thing? I would check that with a mechanical pressure gauge.

 

That gauge looks like it's intended to be permanently mounted inside the vehicle. I have the Harbor Freight gauge kit that's primarily intended as a test gauge. It has a rubber outer shell that makes it a little easier to handle than a dash gauge would be.

http://www.harborfreight.com/engine-...kit-98949.html

It has about a six foot hose on it so you can drape it all the way across to the driver's side to see it from inside the Jeep. Plus you can knock $5 or more off the price with the ubiquitous HF 20% or 25% off coupons.