Anyway, what I want to know is what causes an oil leak? Because today we talked about flushing the engine and he said he's worried that once they do that, that it might dissolve something that could be currently preventing the J30 from leaking oil. Didn't agree or disagree with him because I'm not really sure what makes a car leak oil in the first place. But yep, could someone help me understand?

Bleh, and I'm mad that I didn't get it done too. Gotta deal with another 3 months of sluggish performance :S. Truthfully, if I had more money on me I would've went ahead and did it.

OH, and another quick question. Before I left my dad said to make sure I get 10W40 oil? So when I got there the lady asked what type of oil I'd want in it and I said I think 10W40 and she's like, "Is your oil leaking?" and I said, "No?" Then she suggested to just have 10W30 put in it. Soo, what's up with that?

Thanks in advance X]

1) Statinary oil seals such as oil pan seals should not leak with flush.
2) Rotational oil seal (90% of the oild seals) will VERY LIKELY leak after flush.

I flushed my J30 with BG Engine Purge (solvent based) an year ago abd the camshaft seals started to leak.

If I were you, I will try non-solvent based flush agents such as auto-rx.

Chopper Bob, were you saying that if I get an engine flush that it'd cause the leak? Right now nothing in my car leaks but my dad thinks that nothings probably leaking (the oil) because everything's blocked off by all of the gunk and that flushing will take it away and start causing problems (he's assuming the engine has never been flushed, he's never looked at it). And so the 10W40 means it'd drag more since its thicker? They went ahead and put 10W30 in there so thankfully I didn't insist on the other one, lol. The car right now is dragging enough as it is

Coolyun, so would it certainly not leak if a non-solvent product was used? I'm not sure what they were going to use at Kwik Lube but thanks for the heads up! I'ma ask next time and make sure nothings gonna get damaged.

The front seal is know to deteroriate over time. A new seal is cheap and any competent mechanic should be able to replace it.

http://www.nicoclub.com/FSM/J30/1994_J30/em.pdf

I have a very slow leak only when driving that occasionally hits the exhaust and throws off a bit of smoke.
I assumed it was a leaky valve cover that I plan on addressing soon.
I would MUCH rather tighten the pan bolts than pull the plenum !!

Peopl claim that not only it flush your engine, but it also stop oil leaks in most of the cases.

Someday I'd like to drop the oil pan on my engine, but until then making sure the old oil is hot when it is drained is the next best thing. And sluggish performance is not very oil weight/viscosity dependent at all.

let me see if I can find the post Q45Tech made about it

It's possible depending on where the leak is. Mine is in the front of the oil pan. Tightening the front bolts alleviates it.