Well I thought I'd throw this up since it has been bothering me for awhile now. My 98 XJ has some serious sludge problems, I put new oil in it and after about 100 miles it was midnight black. Took off the oil fill cap and noticed some sludge on the bottom of the head and around the valve springs. So I've been considering running some ATF fluid that I had left over. My question is that would it be alright to run or would I have to worry about the sludge breaking down and clogging my oil passages/journels? Or cause any other damage?

 

Do a couple of oil changes, say under 1500 miles each to flush. Some long runs or highway driving helps. Then do your oil and filter changes regularly after that, 4000 miles. I don't like the solvent flush practices as I would be more concerned of running without lube coverage than running with dirty lube. Do the straight up oil flushes, no snake oil.

 

& change that oil while it's HOT.

 

Alright well thanks for the advice guys. I just picked up some new oil last night and will most likely try this tomorrow. Also why change it when its hot? Would it be because it would have a better chance of the sludge/buildup getting drained out or no?

 

Yes if changed out while oil is hot better for sludge to run out.