They needed that heavy oil to seal the rotary valve. Carbon buildup in the driveshaft housing was always a problem. Later models had sealing rings on the valve that are also used on later V-4, 6 & 8 models. The racing model had roller bearings on the connecting rod big ends and crankshaft mains. Also high compression two ring forged pistons and open exhaust. Several antique "A" racers made high compression pistons the convert the Army-Navy surplus Johnson 10 horse water pump (which had the roller bearings) into a class"A" racer. . . 😀
