If you are a refiner, importer, or producer, you must determine the automotive fuel rating of all automotive fuel before you transfer it. You can do that yourself or through a testing lab.

To determine the automotive fuel rating of gasoline, add the research octane number and the motor octane number and divide by two, as explained by ASTM D4814-15a, Standard Specifications for Automotive Spark-Ignition Engine Fuel, (incorporated by reference, see § 306.13). To determine the research octane and motor octane numbers, you may do one of the following:

Use ASTM D2699-15a, Standard Test Method for Research Octane Number of Spark-Ignition Engine Fuel (incorporated by reference, see § 306.13), to determine the research octane number, and ASTM D2700-14, Standard Test Method for Motor Octane Number of Spark-Ignition Engine Fuel (incorporated by reference, see § 306.13), to determine the motor octane number; or

Use the test method set forth in ASTM D2885-13, Standard Test Method for Determination of Octane Number of Spark-Ignition Engine Fuels by On-Line Direct Comparison Technique (incorporated by reference, see § 306.13).

To determine automotive fuel ratings for alternative liquid automotive fuels other than ethanol flex fuels, biodiesel blends, and biomass-based diesel blends, you must possess a reasonable basis, consisting of competent and reliable evidence, for the percentage by volume of the principal component of the alternative liquid automotive fuel that you must disclose. In the case of biodiesel blends, you must possess a reasonable basis, consisting of competent and reliable evidence, for the percentage of biodiesel contained in the fuel. In the case of biomass-based diesel blends, you must possess a reasonable basis, consisting of competent and reliable evidence, for the percentage of biomass-based diesel contained in the fuel. In the case of ethanol flex fuels, you must possess a reasonable basis, consisting of competent and reliable evidence, for the percentage of ethanol contained in the fuel. You also must have a reasonable basis, consisting of competent and reliable evidence, for the minimum percentages by volume of other components that you choose to disclose.