Are you saying it didn't smoke on the way to the repair shop only on the way home? That would put the question of old gas out of the picture. And it would put the repair shop right square in the picture. No to the exhaust valve sticking you would notice a very bad miss and back firing. I would like to know what the repair shop had to do to fix what ever part of the drive line you had fixed. I'm thinking more like they removed the exhaust system and left it out in the rain.

ITs been sitting for 2 yrs. The gas is old .Change the oil and filter. Fill it up or at least put fresh gas in it. And drive for awhile and let it warm up and clean itself out. If oil and water are not mixing it may be ok and just needs exercised..........

Bad piston rings

Take it back to the shop!!!

95 Jeep Grand Cherokee. It sat unused for about 2 years because of some drivetrain problems. I drove it to a shop a month ago and they fixed it. After I picked it up, it smoked the entire drive home. It didn't smoke when I drove it to the shop. It's white smoke. If I let it idle on my driveway, it will deposit a layer of gray oil on the driveway surface. The grey smoke smells strongly of gasoline when I start it cold.

Could an exhaust valve be stuck in the open position? What else could be the problem? Crankcase oil does not look milky, antifreeze looks clear and green.