XJ Im buying today. Thoughts?

Yesterday after work I went to look at a 93 2 door sport auto with 185k on the clock. Its been sitting for about 4 months, with the occasional start it up and let it run in the driveway every now and then; the owner got a DUI and license revoked blah blah blah.

Anyways, he had it running when I got there which always kinda sketches me out a little. Not expecting much I gave it a look over, drove it around the block, etc. The engine has the normal valve noise these 4.0's usually make, but it did smoke a little. Not much smoke at idle, but once on the gas pedal it did. Not a thick white haze, but enough that its noticeable. Jeep ran at 210 once warm, 4x4 worked flawlessly, interiors dirty and has lots of burn holes. I'm buying this thing today, gonna throw some 31's under it and use it to hunt out of and occasionally drive to work and around on the farm.

How much life does a 4.0 have left in it after it begins to smoke? Can I add some thicker weight oil and possibly slow the smoking down or maybe even stop it? If I wasn't getting the thing for so cheap I wouldn't even waste the time but at the price I cant pass it up...