I suppose if wheels have been neglected then 'extreme' measures are required. However, I've found that good old soap and water on the wheels works just fine, particularly on the SL which probably gets a little better care than the other two diesels that I own.

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Don
'85 500SL (Euro) - 186,000 w/a complete restoration and engine rebuild at 154,000
'95 C280 - 174,000