Hey guys, has anyone ever heard of this? My 96 Cherokee runs great but after running it at highway speeds (65 to 70 mph) for about 30 to 45 minutes it starts blowing blue smoke out of the exhaust. It's quite a lot of smoke too. After I park it and let it sit for a while it doesn't smoke any more. I've talked to several mechanics and I get a different answer from each of them. I don't want to tear into the motor if it doesn't need it. I fell like it's something pretty simple. I replaced the pcv valve. It was pretty clogged but the problem still persists. Any ideas? All suggestions will be greatly appreciated.

 

valve seals could be the culprit here.