Yes..you can add it to oil..or gas..or both..I've only used it as a gas additive and, as said, its been terrific..We leave three vintage cars in Ca. when we come down..1956 Porsche, 1968 Porsche and a 1967 VW Split screen..I fill the tanks and add a little MMO ..seems to keep the damp out and stabilise the gas..do the same with the Thing when we leave here..