CRC PhaseGuard4 Ethanol Fuel Treatment - Don't Trust Ethanol in Your Fuel Tank Without It! CRC PhaseGuard4 is a revolutionary new fuel additive that provides the maximum protection available to prevent phase separation of ethanol fuel with the only 4-in-1 formula that also protects against corrosion, cleans the entire fuel system, stabilizes fuel for long-term storage and restores power and mileage potential. PhaseGuard4 is effective in E10 to E85 fuels and is ideal for all 2 and 4 stroke gasoline powered marine craft as well as autos, RVs, motorcycles, snow mobiles, ATVs, outdoor power equipment such lawn mowers and snow throwers, tractors and other agricultural equipment.