if you have an air compressor and a valve spring compressor you can change the valve stem seals. it cost 12.00 and took me 5 hours. I have an 88 300 e it worked for me 3 yrs and 30,000 mi ago. still good! I use no oil and have 175,000mi . my friend at the benz dealer told me they had trouble with the rubber compound during those years. the replacement seals are much better.... good luck ............john..........................