Jeep 4.0L

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Mar 26, 2004
Got another jeep. 98 Jeep 4.0L 130k, first 100K was put on original owner in 3 years [Eek!] so I doubt he change the oil enough cause that would be like at least 4x oil changes a year w/ a quality oil. Second owner 100k-130k seemed like he was good about maintenance and knew what he was doing. Oil pressure seems decent, it stays at 40psi most of the time, but sometimes will drop to 20 psi at idle in the heat. It does knock some, and you can hear some lifter noise. no obvious leaks or oil consumption I did the first change today Castrol GTX HM 10w-40 w/ an oversided FL-1a Motorcraft filter I also bought some rotella synth 5w-40, but was kinda scared to put that in cause I heard of problems with it clearing out too much crud at once. now for my questions: 1) does Auto Rx seem worth a shot, or a waste? 2) can I mix the rotella t and castrol GTX HM 50/50... or which one is better to run
do you think I need the two bottle treatment or will one be ok? edit: referring to ARX [ July 19, 2004, 01:21 AM: Message edited by: OiledMustangGT ]
I take it you gonna use ARX by your previous post, but to throw-in my own two cents...if this were my vehicle, with no obvious leaks or oil consumption, I'd go over to Wally-World and pick up some Rotella 5w-40 (which you've already done) to use in combination with a FL-1A filter (which you've done as well!). Do not worry about the Rotella cleaning too much...if it makes you feel better, just change the filter out earlier in the OCI! [Big Grin]
I think I'll do a test with Rot. T on my other 4.0L which is used to M1 synth. I just picked up the 4.0L I was referring to yesterday. Drove to check it out, then drove back to my house 400 miles on the interstate [Smile] I think I'll run it for 1500 mi on the GTX and at that point think about ARX.
I've been running the Rotella 5w40 in my '88 Cherokee with the 4.0l. First UOA was nothing special... Sounds fine and holds pressure better when running hot - tend to stay around 50-60 psi running hot versus fading back towards 40 psi when running 5w30 and 10w30. We'll see what the next UOA brings...
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