Originally Posted by Randy Bobani

ATF on the other hand is hilarious. You hear people recommending to add ATF to the engine oil before an oil change to help clean. That makes absolutely no sense. Engine oil contains twice the amount of detergents as ATF. There really isn't much of anything in ATF.

Originally Posted by dave1123

My Grandfather used to use kerosene to clean sludge out of an engine by draining 2 quarts of oil and adding 2 quarts of kerosene, then running the engine for 20 minutes, then draining it. The stuff used to come out in chunks! Personally, I wouldn't do it. This was back in the 50s when engines weren't so highly stressed as they are now.

Originally Posted by awg

I have heard of people recommending some Kerosine as well, so I can only think they are thinking solvent for sludge in the oil pan

ATF does tends to act as a solvent on grease

I have not, and would not, do it

Originally Posted by PatHenry

Have you had the Jeep for the whole 90k whatever miles? Is the head original?

The most likely way a 90k Jeep I6 gets to the point of having bad oil pressure/bearings and talk of needing a new engine is if the 0331 head cracked and someone drove it for a while with coolant contaminated oil.

It sounds like that is what you're dealing with. In which case the engine, despite it's legendary durability and low mileage, is basically sitting in the grey area between Good and Bad. It's running at low, just under min spec, pressure, the block is probably rough but not ruined. Bear in mind that it's not -just- the bearings that were excessively worn, the inadequate lubrication means the cylinders are pretty buggered up as well.

30 weight refers to the second number on the oil rating... like 10w-30, 5w-30. Sometimes it refers to SAE30 (sometimes called "straight 30") which is used in 4 cycle engines typically (aka, push mower, snowblower sort of thing). I'd be using 40 or above on that, so 10w-40, 15w-40.. it's "thicker" oil, more "weight" so to speak. The diesel oil seems a good idea for your situation, especially if you don't have to pass emissions testing and can live with less than perfect catalytic converter function.

I feel your pain on seeing the engine so rough at such low mileage. If I were you, I'd follow the excellent advice of the prior posters and try heavier oil, but I'd also be on the lookout for a potential engine sometime in the future. It may be months, maybe years, that it will run as it is, but it's awful close to failure and if it is a case of coolant contaminated oil damage, it's going to fail at some point and even the block is not worth trying to save. I'd stay calm, keep an eye out for an excellent condition complete 00-01 engine with Tupy/clearwater head or excellent block 80 something - 01 XJ/99 TJ/98 GC and plans to buy a new clearwater head and if you find one, get it and store it until your current engine fails, or replace it when conditions are right preemptively.

Just my opinion. Don't panic or give up on the Jeep... an engine swap is not as bad as you might fear and you don't need to be a professional wrench turner to do it yourself on these Jeeps.

Originally Posted by RocketMouse

I challenge someone to give me a repeatable example of another motor that can stand up to that level of internal damage and literally keep working. I think it would be hard pressed.