Unleaded aviation gasoline. An unleaded aviation gasoline includes a blend of high octane alkylate, an effective amount of selected alkyl benzenes, and selected aromatic amines sufficient to improve the functional engine performance to avoid harmful detonation sufficient to meet or exceed selected standards for detonation performance requirements in full scale aircraft piston spark ignition engines designed for use with Grade 100LL avgas. Suitable alkylated benzenes may include a mixture of xylene isomers. Selected aromatic amines, such as N-methyl-p-toluidine, are used to increase performance. The high octane alkylate may be an aviation alkylate, or iso-octane, or both, and may utilize high octane alkylates having a motor octane number of between about ninety-seven (97) and about one hundred (100). Suitable amounts of iso-pentane, n-butane, and iso-butane may be used for providing vapor pressure in a commercially acceptable range.