Universal 200ML Cylinder Oil Catch Can Tank 5"x3.25"x3.25" with Breather Filter & Dipstick PurpleAn 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