A rotary combustion engine with one or more working units, which include a peripheral housing, a front housing plate, a rear housing plate on the output side, an eccentric shaft, and a piston, where the eccentric shaft includes an eccentric, and front and rear sealing parts. Lubricating oil is conveyed by an oil pump from an oil tank through the eccentric shaft to first and second main bearings, and to an eccentric bearing, from which a bevel on the front sealing part conveys it to a piston space, from which it is conveyed by way of a bevel on the piston and a rear bevel back to the oil tank to close the oil circuit. The bevels direct the oil circulation from the front of the working unit to the rear, reduce splash losses, and increase the cooling action on the internal surfaces of the piston.