(a) In the case of gasoline, if you do not blend the gasoline with other gasoline, you must certify the gasoline's octane rating consistent with the octane rating certified to you. If you blend the gasoline with other gasoline, you must certify consistent with your determination of the average, weighted by volume, of the octane ratings certified to you for each gasoline in the blend, or consistent with the lowest octane rating certified to you for any gasoline in the blend. Whether you blend gasoline or not, you may choose to certify the octane rating of the gasoline consistent with your determination of the octane rating according to the method in § 306.5. In cases involving gasoline, the octane rating may be rounded to a whole or half number equal to or less than the number certified to you or determined by you.
(b) If you do not blend alternative liquid automotive fuels, you must certify consistent with the automotive fuel rating certified to you. If you blend alternative liquid automotive fuels, you must possess a reasonable basis, consisting of competent and reliable evidence, for the automotive fuel rating that you certify for the blend.
(c) You may certify either by using a delivery ticket with each transfer of automotive fuel, as outlined in § 306.6(a), or by using a letter of certification, as outlined in § 306.6(b).