The unique design of the Wankel rotary engine creates some special problems in lubrication.
During our trials, we noticed that the best commercial motor oils for conventional 4-stroke engines are inadequate for perfect lubrication of the Wankel rotary engine and do not obtain mechanical performances on this type of engine.
To lubricate the Wankel rotary engine, one part of the oil is injected in the air-fuel mixture, to lubricate the wall of the epitrochoid surface and the seals. Another part is circulated on the shaft bearings and is used to cool the rotor.
In both cases, problems to solve are different, and the lubricant is necessarily a compromise to meet the different requirements.
At this stage, the best lubricating oil is a synthetic mineral oil blend with an appropriate combination of additives. The synthetic oil is a petrochemical product made by polymerization of a monoolefin C4 cut; the molecular weight is in the same range as the conventional mineral oils.
With such a lube oil formulation, deposits in the combustion chamber are reduced to a minimum, avoiding preignition and seal sticking. Apex seal wear has been drastically reduced and engine life is longer.
The performance of such a formulation has been tested in water- and air-cooled engines, on the bench and in the field.