Mississauga Lincoln car dealer changed oil+filter went home in 25 km white emulsion deposits are back. Dealer says he checked other cars in the shop and 3 had deposition on the oil cap. The engine oil was showing no contamination even before it was changed. I checked with a mechanic i personally know and he said probably a head gasket leak, a small leak to be sure.If not the head gasket perhaps the PVC valve is blocked.hen the oil was changed I wiped the oil cap clean and drove 20 km and the deposition is back. I am thinking the dealer has had a confidential memo about head gasket failure and has chosen not to do anything about it as the cost to repair the engine, head distorted, the block possibly distorted is very expensive and opens the dealer to admitting a factory defect on this engine.I noticed that everyone in the dealership knew about it, rather unusual.Just reassure the customer and send him home was the impression I got. message from Jim in Mississauga. Yes the weather is cold, and yes some moisture is always produced normally, my 2005 GM Avalanche oil cap is as dry as a bone. The cars are driven in the same climate and frequency. Any input would be really appreciated. Thanks