16 CFR Part 306
The Fuel Rating Rule requires that refiners, importers, and producers of certain automotive fuels determine the fuel ratings before transferring the fuels to a distributor or retailer. For gasoline, the fuel rating is the octane rating. For alternative fuels, other than biodiesel, the rating is the minimum percentage of the principal component of the fuel. For biodiesel fuels, it is the percentage of biodiesel or biomass-based diesel in the fuel. The Rule also requires retailers to post the fuel rating on their pumps.