Unleaded aviation gasoline

An unleaded aviation gasoline composition which comprises a blend of at least about 80% by volume of aviation alkylate gasoline, up to about 10% by volume of a gasoline-soluble dialkyl ether gasoline blending agent, from about 0.3 to about 0.5 grams of manganese per gallon as at least one cyclopentadienyl manganese tricarbonyl compound, and optionally up to about 15% by volume of aromatic gasoline hydrocarbons with the proviso that the components of said gasoline composition are selected and proportioned such that said gasoline composition possesses at least the following octane qualities and heat contents called for by ASTM Specification D 910-90:

• (a) a minimum knock value lean rating octane number of 100 as determined by ASTM Test Method D 2700 and wherein Motor Method octane ratings are converted to aviation ratings in the manner described in ASTM Specification D 910-90;
• and (b) a heat of combustion as determined by ASTM Test Method D 1405 and as calculated from Table 1 thereof of 18,720 Btu per pound minimum, or a heat of combustion as determined by ASTM Test Method D 2382 of 18,700 Btu Per pound minimum, the latter method controlling in case of a discrepancy therebetween.