Mercedes did not recommend using synthetics in any of their motors until the M112 and M113 engines were released in 1998.

That's not to say that you can't use synthetic; it's just that the factory never recommended it in any of the engines prior to 1998 (including the M104's that were used in the S class until 2000).

In the Sep / Oct. 1997 issue of the Star Magazine, Stu Ritter and George Murphy (technical editor and vintage editor) discuss this issue and are against switching engines designed to run on conventional oil to synthetic.

While no damage will likely result, they discuss how synthetic oils are hard on seals, and how if left sitting, synthetic oil can lead to hydraulic valve lifter clatter. The valve lifters can de-pump due to the thinner synthetic oil leaking out or bleeding out.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".