Milky oil under the filler cap — causes

A milky, beige film under the oil filler cap can be frightening. Sometimes it’s a harmless effect of condensation, and sometimes a sign of a more serious fault.

The most common cause — condensation

On short trips and in the cold season, water vapour condenses and mixes with the oil at the cap. After a longer drive, once the engine warms up properly, the film usually disappears.

When is it a serious problem?

• A milky emulsion over the whole dipstick, not just under the cap
• A drop in the coolant level
• White, sweetish smoke from the exhaust
• Engine overheating

Such symptoms can point to a damaged head gasket — then diagnostics are needed. If in doubt, we’ll help assess the situation.