ccording to Pete Paraska, there are three ways oil can get into your intake:
- (1) Through the positive crankcase ventilation (PCV) valve.
- (2) Through the hose leading from the valve cover to the intake pipe.
- (3) From an leaky oil seal in your turbocharger.
#1 is true regardless of the age of the valve.
#2 is a symptom of blow-by, where oil is getting past the piston rings.
DSMers often install oil catch can [[What is a catch can?] in an effort to keep oil out of the intake.