My 300sdl burns oil badly every once in a while. The car drives and runs fine but puts a cloud of blue smoke out, then it will clear and be fine for a period of time not smoking at all, then go back to smoking badly. My mechanic replaced the turbo with a rebuilt and was sure that was the problem. The car was fine for a week and then returned to smoking. It does not matter if the car is warm or not, sometimes it smokes badly and other times not at all. Any ideas would be greatly appreciated.