Hello together through my Zk weckersel oil is supposed to have come into the cooling medium. In addition through def. oil cooler has come again oil into the cooling system. VW has cleaned with its own medium cooling system but still get oil into the cooling medium. It is black oil and no white mud. Compensation tank is below red and above full oil. VW has pulled the system and it was no pressure loss to notice, so dense. Now I want to rinse the system myself. What should I rinse with and where should I wash the I don’t want to use detergent because it can foam later. I don’t want to buy the detergent from ATU should have a bad call. What suggestions do you have? Would you like to sell the car and therefore it should be technically ok and also be bought without any concerns. MFG NIHAT