This is a very interesting discussion, and for me particularly since I happen to own all three vehichles in question.....the C-class ('96 C-220); The E-class ('86 330E) and the W140 S-class (500SEL). I will try and coalesce my thoughts on the subject and add my two cents (three, with inflation) tomorrow or Friday....as if anyone really cares...who knows, maybe you do!

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1996 SL320 97K miles
1996 C220 130k miles
1992 500SEL 170k miles <---sold
1986 300E 216k miles <---sold