for starters this site is killer! I bought my 96 XJ a few months back,had never thought about jeeps but saw 1 cheap 4sale and bought it and I LOVE it!! I'll buy another in a heartbeat when this one goes to my back 40 to it's final resting spot so I can pay my respects once a year...anywho it has 147k runs mechanically sweet and was taken VERY good care of before me, it looks like new so I think the motor in good shape(it's very quiet and smooth no weird vibrations or noises)and it is the 2.5/4 banger (which Im ok with its spunky no 4.0 but impressive for a 4 cyl. and good on gas....some day I'll get a 4.0 XJ they go great from what I saw and that was and old 4.0HO) I want to run synthetic oil because of the performance and superior protection of it but is 147k to many miles to start running it from worn bearings or should they be in good shape still I was told in automotive school years ago with excessive clearance on the bearings the thinner synthetic oil wouldn't supply enough oiling to keep the bearings from pounding and thus a spun bearing, or should I stick with regular quality oil? Any imput would help thank you...

I wouldn't worry about running synthetic in an engine from a mechanical viewpoint anytime. The only question in my mind is whether you will benifit from it's use in the engine. Most people do not achieve the full benefit of synthetics because they change the oil too often to max out the cost benefit. That said, you will not damage anything by using it.

Using a quality dino based oil IMHO is likely more than sufficient in an engine that gets regular oil/filter changes unless you run in extreme cold or hot opperating conditions. For your weather on the east coast, use good 5w30 oil year around and you will be fine.

Some do say that the synthetic will leak more if there are weak seals or gaskets but I have yet to see that confirmed in modern engines other than stories and those more than likely were previously under maintained .

So long as you are maintaining n 10 psi or more when warm at idle and have about 30 at running speeds you are good to go.

Where I believe the most benefit from synthetics for the jeep is found is in the power train. Running synthetic in the diffs and in the transfer case will benefit in reducing heat and in operating cold. Same goes for the 5 speed and the automatic. Thats where I would make sure to use the synthetic.

If you want to spin your head around in oil some :iceslolan check out this site - http://theoildrop.server101.com/ubb/ultimatebb.php :smokin:

JD

Right on, synthetics definitely won't hurt, and I've heard the same stories about leaks when switching to synthetics on a higher mileage vehicle, but do not know from experience whether or not it's true.

Another good oil site:

www.bobistheoilguy.com