Yamaha's ACC-RNGFR-PL-12 Yama lube Ring-Free Fuel Additive improves power and efficiency in two and four stroke engines. It removes and prevents carbon and varnish deposits from injectors, carburetors, intake valves, intake ports and combustion chambers. These deposits are caused by poor fuel quality. It even fights corrosive elements of sulfur in Ethanol blended fuels. Use with Yama lube Fuel Stabilizer and Conditioner PLUS to prevent any harmful effects.