Is the sump pressurised?
 

I have a mate who says that the rubber seal at the top of his dipstick is perished. He is concerned that oil will be forced up out of the dipstick.

I was under the impression that oil in the sump just drains back down there and is not under pressure. Am I right?

most cars have a crankcase breather to vent any pressure. there maybe a bit of blowby from the rings and the crank wizzing about will all create a bit of pressure. so yes it is possible to get oil blowing out the dipstick :)

2 O Rings on the dipstick, worth replacing both.....