Sea Foam® is a safe and versatile additive that can be used in fuel, oil or added directly into the combustion chamber on 2-cycle, 4-cycle, rotary and diesel engines. Sea Foam® is a 100% pure petroleum product, so it is as safe for seals, o-rings, sensors and other fuel system and engine components as the fuel or motor oil that runs the engine. Sea Foam® contains NO harsh chemicals.