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Mayo like stuff in oil filler


New member
5 May 2003
I went to top up the oil in my car today (996 C4S). When I took off the filler cap, I noticed that the inside was covered in a thick, yellow substance like mayonnaise or custard.

Should I be worried??

The car also appears to be using a lot of oil.

Any suggestions?



Migration info. Legacy thread was 11629
Sounds like your coolant is leaking into the engine casing and mixing with the water, hence the "Mayo".

Early 996 blocks were prone to going porous, but I thought Porsche had erradicated the problem, better take it back to the OPC

Migration info. Legacy thread was 11633
Neil. Yeah it sounds serious. If the car has sat for a while unused, or used for only short journeys it is possible it is just a bit of condensation in the engine, but it is more likey coolant in the oil, as Poon says. Definitely a trip to the OPC.

Migration info. Legacy thread was 11634

thanks for the feedback.

Booked into OPC - I'll let you know the outcome.


Migration info. Legacy thread was 11773
Neil although it could as Poon suggests ( worst case) 996 are prone to producing this type of junk on the filler cap if you don't drive far enough and fast enough to burn of wter vapour.

Migration info. Legacy thread was 11779
Old forum user Unidentified(11139) wrote:

mine does this, i use it every day for very short journeys of around 4 miles. Everyone i've spoke to says the same thing, thats its bound to generate condensation as you're not getting the car warm enough to burn it off, plus the filler cap is so far away from the engine there's no way it can be a water/oil problem or it would appear on the dipstick.

If you get custard streeks on the dipstick - be worried, in the filler tube - no worries just clean it out.

Migration info. Legacy thread was 131834
Classic short journey syndrome !

Effects most cars if you only drive for short journeys all the time, as the engine never fully heats up with a run for a sustained duration

Migration info. Legacy thread was 131883
As Admin says, mayo in the oil filler cap is a sign of moisture mixing with the residual oil in the neck of the cap... the car isn't being run enough/hot enough to evaporate the water in the neck filler.

Migration info. Legacy thread was 131927
Beware what the OPC say.. They may want to cover themselves BUT I have heard both sides of the story.. Definately mine has 'small' amount of mayo when not used much .. It's emmulsification of water & oil.. Particularly this time of year when there's dew in the mornings a small ammount of moisture in the form of condensation is bound to lie in the filler pipe/cap. More importantant is to check if there's OIL globs in the Water.. On many cars this is sign of head gasket or pourosity. Also I think it's made more a problem with the filler cap lying flat.. The people with great experience in this are Autofarm

Good luck and don't loose sleep until you know for sure if there's a problem. There's a lot of hype out there !

Migration info. Legacy thread was 132099

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