bengerman, if the valve stem seals are worn oil is leaking into the combustion chambers/cylinders and being burned while you drive ... that's creating the blue smoke from the exhaust pipe. As mentioned your engine likely needs new valve stem seals. How do the spark plugs look? Unless you are an experienced DIY mechanic it's probably a good idea to take your car to a reputable MB-trained tech for a diagnosis and repair estimate.

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Fred Hoelzle