Back when I worked for a Chevy dealer we had a kid drain the transmission, and double fill the oil on an Aveo. Customer brought it back 30 minutes later, smoking horribly. We drained the entire thing, then let it run for a day to get rid of all the extra oil residue that had built up in the vehicle/exhaust. Basically it needed to have all that extra crap burnt off. It was completely fine. Now is this car an Aveo? No. But the same thing happened, to a degree.