The expediency and effectiveness of use of composite compositions for raising the octane number of straight-run gasoline fraction are proved. It is shown that cellosolves and carbitols tested as oxygenate additives improve the antiknock properties of narrow gasoline fraction selectively, depending on their fractional composition, and significantly raise the octane number of a straightrun gasoline fraction. A synergistic blend of glycol ethers at determined optimal ratios can be used to get high-octane gasoline with an octane number not lower than 93, which is of interest as a highoctane component for compounding motor fuel. The low composite additive concentration (1 vol. %) in gasoline hardly has any influence on change in the basic performance properties of motor fuel and primarily on the fractional composition. Use of such an additive is preferred to existing antiknock additives for solving important economic, technological, and ecological aspects of the use of motor fuels in modern automotive engines.