A hydrostatic displacement engine having pistons which slide on the inside of a stroke ring. The eccentricity of the stroke ring, relative to the cylinder block, is variable. The interior of the housing is divided in two areas which are separated from each other preferably by a seal, namely in the area located radially outside the stroke ring and the area located radially within the stroke ring. The inner and outer areas serve as a leakage oil collection space and connects through a leakage oil line with a pressureless liquid container. Emptying in the area situated radially outside the stroke ring is a connection line which is supplied by a pressure supply. A pressure valve maintains the pressure in the outer area at a value of several bars.