White paste on the dip stick or oil cap or milky in oil can tell you that you have coolant mixed in, and most of the time causes by leaking head gasket. Spark plugs can tell you whether you have coolant mixed in. It happened to my bimmer as well when the head gasket went south. However, i really don't think you have a bad gasket. Another way to check for a bad gasket is look inside your coolant reservoir for any little bubbles or oil. Hope nothing serious, but you'd better to have it checked.