Some of our customers have seen a white, milky substance (sometimes described as foam) in the area of the oil filler neck or dip stick. What is this stuff?
ExxonMobil: This white, milky substance is an emulsion formed on the surface of the fluid or an oil-wetted part and indicates the presence of minute amounts of water mixed with oil. It is probably harmless. To be sure, you need to make sure you do not have water in your oil. You can do this by asking your oil analysis lab to test a sample of your oil for water (If you are not analyzing your oil, we can send you a test kit). If the lab indicates you have water in your oil, replace the oil with fresh oil. If the lab indicates that you oil does NOT contain water, then the emulsion you are seeing is harmless and is the result of condensate in at least this part of the engine. This kind of phenomenon has been observed in engine oils that contain potent dispersants and rust inhibitors, as present in Aviation Oil Elite 20W-50. Condensation can occur even when an engine is stored in a warehouse, or where humidity is relatively low. One of the products of combustion is water vapor. Hot air arou
