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Fuels and Fuel Additives

Fuels and Fuel Additives Registration

Regulations & Standards

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Substantially Similar

  • Substantially Similar and Clean Air Act 211(f) Waiver Regulation Information

    The term "substantially similar" is used in section 211(f) of the Clean Air Act to distinguish which fuels and fuel additives are prohibited by this section. Fuels and fuel additives which are prohibited may apply for a waiver as described in 211(f).

  • Regulation of Fuels and Fuel Additives: Revised Definition of Substantially Similar Rule for Alaska (published April 25, 2008)

    Discussions with an Alaskan refiner highlighted the need for an amendment to the substantially similar provision of Section 211(f) of the Clean Air Act for unleaded gasoline to improve cold starting of vehicles in Alaska during the winter months. Previously, manufacturers of gasoline for Alaska could not use a temperature below 41 degrees Celsius when testing the vapor-liquid (V/L) ratio of the fuel and still be within the definition of "substantially similar." This amendment allows manufacturers producing unleaded gasoline for use only in Alaska during the winter months to use a minimum test temperature of 35 degrees Celsius when testing for a maximum V/L ratio of 20 instead of requiring a V/L test temperature of 41 degrees Celsius.


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