Yellow 'mustard' or 'mayonaise' around filler cap

[Craigus]

I know this can be the sign of head gasket failure, but the car I went to see today had a slight hint of this around the filler cap. The guy is selling the car as he doesn't use it and it has been standing for quite a while, so does that have something to do with it? Is it just condensation in the oil? Is that anything major to worry about?

It wouldn't start when he tried to either so had to jump start it, presumably that means it's just the battery and nothing else?

It is on an E46 328i (petrol) 1999.

 

[Russ_16v]

Yes, it could be just condensation, but I would have a feel inside the rocker cover through the filler hole, and see if you can feel any more on the cover itself - Id also wipe off the cap, nice good test drive to get it warm, then check again to see if it has come back.

Also check inside the rad for any signs of oil.