Dura Lube Severe Fuel System Cleaner is precisely formulated to clean the entire fuel delivery system, including fuel injectors, carburetors, valves, ports and intake manifolds. It also helps remove valve stem gum. A cleaner running engine helps improve fuel mileage. This cleaner is compatible with all grades of gasoline fuel, including E-10, E-15 and E-85 Ethanol blends. It is not for use in diesel engines. Dura Lube Severe Fuel System Cleaner will not harm catalytic converters.