An unleaded gasoline composition comprises, based on the total volume of the unleaded gasoline composition, 50 to 96 vol. % of an unleaded gasoline; 2 to 20 vol. % of a mixed butanol; and 2 to 30 vol. % of a distillate oil fraction comprising a paraffin, an olefin, a naphthene, and an aromatic at an initial boiling point cut of 180° C., wherein the unleaded gasoline, the mixed butanol, and the distillate oil fraction are selected to provide the unleaded gasoline composition with a Research Octane Number of 90 to 101, determined in accordance with ASTM D 2699; and a Motor Octane Number of 81.4 to 90, determined in accordance with ASTM D 2700.