What does white residue around the oil filler cap mean?

My Volkswagen Golf 2002 has white residue around the oil filler cap, is this always a sign that the head gasket has failed?
Not always. Depends how the car is used. If it does a lot of short runs from cold starts then the mayonnaise is from emulsified oil under the cam cover. If the car is regularly driven significant distances of 50 miles or more then there is a possibility of head gasket failure, but two other symptoms of that are coolant blowing out of the expansion chamber cap and a drop in the level of coolant in the expansion tank.
Answered by Honest John on

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