Here`s the deal:
The oil filler cap is the highest point on the engine, so all vapors naturally migrate there, and condense as the engine cools down. This constant cycle is what causes the infamous "BMW mayo". Cars that make mostly short trips usually have a more pronounced version of this condition.
The road goes ever onward....
*Please support the Wounded Warrior Project*
When faced with choosing between two evils, always go with the one you`ve never tried before....