All German cars get that goo. I had a terrible problem with it on the BMW. My thermostat was stuck open! Engine never got past the blue. I was cleaning the lid every day along with the inside of the block (as far as I could reach). Repaired the thermostat and changed the oil the next day (while it was at its hottest). Then I drove to Nebraska and back last weekend. No moisture at all!! Checked my Mercedes, same thing. I take that out for a 30 to 45 mile drive a week to keep it clean. Work pays mileage!