An oil capturing device for capturing oil from crankcase gases. The oil capturing device includes a housing containing a central chamber and a rotor disposed in the central chamber. The rotor includes a shaft rotatable about an axis and a flange extending from the shaft towards the inner wall of the central chamber. The flange is in contact with the inner wall, and spirals along the shaft so as to define a gas passage interconnecting the inlet to the first port. The gas passage provides a passage for crankcase gases to flow from the inlet to the first port, and narrows as it proceeds from the inlet to the port so as to compress crankcase gases travelling from the inlet to the first port. The rotor may be operable by a motor, pulley connected to the engine, or a turbine driven by the engine's exhaust.