I have a 1995 Audi A6 Quattro that has been running fine ever since i got it, yesterday i took it to Jiffy Lube to get my fluids topped off after driving around all day. they said my oil was fine and filled my wiper fluid....well about an hour later my car overheated and wouldn't stop. then it started blowing thick oil smelling smoke out the tail pipe.....whats wrong and what should i do????