An oil catch tank/ can is used in t

An oil catch tank/ can is used in turbo applications, or high-performance racing applications where excessive blow-by (leakage past the piston rings) of air and fuel vapor occurs. This creates a positive pressure in the crankcase. During engine operation, blow-by gases, as well as oil mist from the rotating components of the engine, pass through the PCV valve and are routed back into the intake for the engine to burn off. However, some of the oil mist and other by-products settle along the engine intake and over time form a gunk. The oil catch tank collects such oil mist and condenses the fuel vapors while allowing cleaner gases to be passed back into the intake.