An engine Oil leak may develop from the PCV vent housing on the valve cover and/or the inspection plate on the front of the engine.Google+
Car Problem Reports
Mercedes-Benz C43 AMG Oil May Leak From PCV Vent Housings and Inspection Plates
Mercedes-Benz C43 AMG Problem
Visitor, 1999 Mercedes-Benz C43 AMG, 55,000 mi
oil leak from valve cover and inspection plates.
Fixed by replacing valve cover gasket and reseal inspection plates.