I have a 89 YJ with the 4.2L. Its using oil, around a quart every 300 Miles. Its not burning it, its not leaking. Theses no puddle on the driveway, the pressure sending unit seems to be holding oil. The only thing I can think of is the round vent like thing on the top of the valve cover behind the fill cap puffs out a little smoke. Almost like a little train engine. Is that supposed to happen? That's the only possible cause of it using oil that I can see. Any ideas on why its using the oil? I read that a lot of times it is the pressure sending unit leaking, or a blocked breather tube. Is there a breather tube on the 4.2L? I looked real quick on the engine but didn't see anything. But if that is clogged that would maybe cause the oil to vaporize out of the vent on top, maybe? Ideas would be helpful.