Abstract: A lubricating system for bearing shafts and the like, for example, in a gas turbine power plant especially for an aircraft, has an oil-air separator which is vented to the atmosphere. A pump wheel is used for the separation of the oil and the air out of an oil-air mixture. The pump wheel is so constructed that centripedal and centrifugal forces are employed for the oil-air separation. The air passes by centripedal force through a sponge type filter structure and out through a hollow central shaft carrying the pump wheel or forming an integral one-piece component with said pump wheel. The oil does not travel through the filter but is reversed in its travel direction by centrifugal force for return into the lubricant circulating system.