I have a 2002 Jeep Grand Cherokee 4.0 with 80,000 miles on it. While driving my oil pressure sits around 40 and at idle it sits around 20. I have hat the engine block tested and that was fine. The oil pressure sending unit looks newer. Everything sounds normal when driving and at idle so I'm not sure whats going on. Does anyone have a good suggestion?

 

Your pressures are normal. Spec for the 4.0 is no lower than 13 PSI at hot idle. For an accurate measurement, hook up a mechanical pressure gauge.

 

Normal. Don't sweat it.

 

Agree, looks normal - my 2000 WJ 4.0 has about the same pressures on a 78k mile engine.

 

Yeah, everybody asks me what I did to mine and I tell them nothing but normal maintenance and switching to 10W-30 because I have 40 at idle hot and 55 at 65 mph with 227K miles on it now. I did replace the sending unit with a Mopar one though.