| primary reference fuel [`prī´mer·ē `ref·rǝns ´fyül] MATERIALS 1. Gasoline; isooctane, n-heptane, or mixtures thereof used in the American Society for Testing and Materials-Cooperative Fuel Research gasoline test engine to determine the octane rating of commercial gasoline. 2. Diesel fuel; cetane, α-methylnaphthalene, or mixtures thereof used in ASTM-CFR diesel test engines to rate the cetane number of commercial diesel fuels. |