Last post on Oct 07, 2010 at 1:03 AM
You are in the Jeep Cherokee and Jeep Grand Cherokee
What is this discussion about?
Jeep Cherokee, SUV
#2 of 3 Re: 1991 Jeep Cherokee- General questions on my first Jeep... [aislinmmh]
Jun 21, 2008 (6:21 am)
The 4.0L I6 engines are notorious for oil pump failures. If your oil pressure gets below 30 pounds at idle then you have a bad oil pump. By the way, your Jeep takes 10W30 oil (don't listen to people who tell you to put in 10W40 or synthetic!) If I were you I would sell it due to signs of neglect.
#3 of 3 Re: 1991 Jeep Cherokee- General questions on my first Jeep... 
Oct 07, 2010 (1:03 am)
This is a very old post, but wanted to put in my two cents for anyone who ran across it later. I have to disagree with the previous post. For the notorious oil pump failures I have owned 4 Jeep Cherokee's with the 4.0L engine, 2 that I ran well over 200,000 miles and none of them ever had an oil pump failure. On the oil pressure, I was looking in the shop manual for a Cherokee that was a year or 2 older and in the shop manual it said that at idle (600rpm) that the oil pressure should be around 13psi and at operating (2000rpm) that the oil pressure should be between 35-75. On the oil it depends on the temperature that you will be driving the vehicle in, 10W30 (I believe) is what the manual recommends for all around weather.