I am having the same problem...oil coating along the underside of the driver's side of the car. Have you checked your oil filter housing gasket? Didn't seem to be the problem on mine, but it could be on yours.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine