Do NOT lubricate the gas system piston, with anything. This mechanism is designed to operate DRY. If you put a lube, especially one with the consistency of motor oil, you will have a baked-on coating on the piston. I am not against motor oil for the other moving parts, such as the op rod and bolt. In fact, tests have shown Mobile One to be an excellent lube for the moving parts of many gas-operated firearms. It adheres to metal surfaces real well. But, the lubrication process does not include the gas system piston of an M1A. Leave it dry.