Octane data is presented for a range of high octane fuel components and potential blending formulations for unleaded racing fuels with research octanes in the 110 range intended as suitable commercial replacements for leaded racing fuels.Data is reported on the antiknock response for organometallic additives containing manganese and iron, in this octane range. Octanes were determined for families of selected compounds including ethers, esters, amines, alcohols, hydrocarbons and miscellaneous chemicals formulated with a base blend of toluene and refinery alkylate hydrocarbons. Dynamometer test data is also presented.The results indicate that the blends producing the highest octanes contained either oxygen or nitrogen bearing compounds and were capable of producing octanes in the 110 range. However, for a potential unleaded fuel, only a limited number of materials were able to meet the key criteria of safety, trouble free operations and a fuel switch requiring only minor engine adjustments or none at all. The oxygenate methyl tertiary buthyl ether (MTBE) and a manganese additive methyl cyclopentadienyl manganese tricarbonyl (MMT) ranked high as preferred blending agents for an unleaded racing fuel.