On my 2001 Jeep Cherokee 4.0L, I have noticed that my oil pressure gauge is not consistent. When I first start up, it reads right in the middle, or to the right of middle, but as the engine warms, and I'm at low RPMs, the pressure seems to plummet, and the gauge shows about 20 PSI. When I am moving again, it's right back up in the middle.
Is it a problem with the sending unit, or something much worse? The engine has 58,600 miles on it, and this engine is known for high mileage capability.....
Any help is appreciated,
Joe