I have just had a valve job done where all the seals were replaced. I get the car back and take a trip and now the consumption has tripled. I take it back to the MB shop and they check all the seals again. #2,3,4 plugs are getting excessive oil on them. He replaced a seal again(not sure if one was bad) and changed the plugs. A day later the car is missing and one episode of smoke came out the back exhaust. I pulled those same plugs and #2 is charred on the end and it along with the others listed above had oil signs. I am wondering if my problem might be piston rings? Does anyone know?