scope:

Definitions.

As used in this part:

(a) Octane rating means the rating of the anti-knock characteristics of a grade or type of gasoline as determined by dividing by 2 the sum of the research octane number plus the motor octane number.

(b) Research octane number and motor octane number. These terms have the meanings given such terms in the specifications of ASTM D4814-15a, Standard Specification for Automotive Spark-Ignition Engine Fuel, (incorporated by reference, see § 306.13) and, with respect to any grade or type of gasoline, are determined