I too had this problem... white gunk on the dipstick, this is obviously pretty alarming as you start to fear the worst. Some type of leak between the cooling system and the bottom half of the engine!

In my case it was actually a bad vacuum hose that had ruptured and allowed the engine vacuum to pull atmoshperic moisture into the crankcase. The hose was between the turbo and the engine ('95 854T).

I should have known it was vacuum related, the mechanic couldn't it out, but did confirm that it wasn't engine coolant. I should have suspected the vacuum leak because my brakes were needing more and more pedal effort... was losing the vacuum assist.

This problem was actually diagnosed by a garage trying to fix an oil leak from the back of the engine that was getting all over the underside of the car and burning oil on the exhaust. They spotted the ruptured vacuum tube and a bad oil return tube between the turbo and the engine. I hope this return tube fixes my oil leak problem.

My car has 160K on it, but I want to keep it for well over 200K.