A self-powered centrifugal separator, for separating particulate contaminants from a liquid lubricant of an automobile engine, includes a rotor container rotatable about an axle to which it is journalled by bushes. When the engine is running, a film of pressurized liquid between the bushes and axle lubricates them and provides radial stiffness, but when the engine stops and liquid supply ceases, radial stiffness is reduced and the partially emptying container may vibrate and create wind-down noise. At least one bush, which normally provides a horizontal thrust bearing to support the weight of the container at low speed, has, with the axle portion it surrounds, a region tapering in diameter to center the container with respect to the axle and provide both radial and axial support.