I think the chart that tells you is in the owners manual. It goes by temperature. What's the hotests and coldest weather that you get? When the wife gets back from the store I can look it up. I personall use Valvoline 15W40 for both the 1997 C230 and 1994 E320 (and make sure the brand meets the rating criteria (some crazy codes) that the book spells out. It's nice that both engines take the same oil.

One of the other forum members put up this link... http://mywebpages.comcast.net/x0rr0/MBASP.pdf

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Michael

1988 300 SL (5 Speed)
1994 E320 Wagon
1997 C230