oil pressure?

Lots of people out there own Jeeps.
Here is another question that has been shot my way.

I have a 91 Cherokee, 4.0L with 180,000 miles oil changed regularly at 3000-3500 miles using Castrol 5w-30, my concern comes from the oil pressure gauge. When first starting the vehicle it will take about 20 seconds for the pressure to come up, usually to about 40psi. After driving, at highway speed (70-75), when stopped the pressure will drop completely down to the bottom. The motor makes no discernable change in sound or feel. My question is, could this just be a problem with the gauge or sending unit, or should I just bite the bullet and change the oil pump? Other than this recent issue the thing runs great, so trashing what is otherwise a good vehicle is not really an option. Thanks in advance for any advice.

Any ideas out there guys/gals?
Lester

For that kind of mileage and engine, 5w30 is a bit thin for all, except the coldest winter day. Try 10w30 in winter and 10w40 in summer and see how the pressure changes.
However, a new oil pump is inevitable. Why risk an otherwise sound engine?

i have the exact same problem with my 2000 sport. please help if you hear anything [email protected]

PCV system! Get it checked. Had a similar problem, I originally thought it was my head gasket that had gone cuz oil seemed to be coming out everywhere. Turned out the PCV (pressurized crankcase ventilation) system wasn't moving the oil around, so that the inside of the engine was getting too pressurized so that the oil was coming out of any crack it could find.

The PCV stuff is when you are looking under the hood, the first hose coming off your valve cover, leading to the air filter.

Should be less than $100 for dealer parts.

hope that helps. I'm not sure where it is on the 2000, but it's an affordable starting place to troubleshoot.