Oil cleaning assemblies for engines

In a centrifugal separator for liquid media which includes a casing, a base plate connected to a lower end of the casing with discharge nozzles mounted in said base plate, a central tube extending through the base plate, upwardly into engagement with an upper part of the casing, and a separation cone in the form of a downwardly facing frustum of a cone, an upper radially inner rim of said separation cone being spaced from said central tube to thereby define an exit passageway between the separation cone and the tube, and a lower radially outer margin of said separation cone being attached to a lower rim of the casing throughout the circumference thereof and substantially adjacent the base plate so as to define an upward and inward flow path over the separation cone from said casing towards said upper rim, the improvement wherein said separation cone is provided with a plurality of generally radially directed and upwardly projecting ribs.