I’ve just been sent a photo of a Porsche 996 oil filler neck, showing a build up of yellow sludge. This is, in fact, an emulsion of oil and water. It can look alarming but is usually nothing to worry about.
The 996 engine has a long filler next and condensation can build up in this, especially if the car is rarely used or only used for short journeys. The moisture mixes with the oil to create the sludge.
Occasionally, though, it can point to a more serious problem. Namely that the oil and coolant are mixing with each other. So,do check the dipstick for evidence of moisture,and that the coolant tank is oil-free and at the correct level. If in doubt, take the car to your local Porsche specialist to be given the once over.