Alkenyl succinimides with different alkyl chain lengths have been synthesized. Alkenyl succinimide samples based on polyisobutylene with molecular weights of 1000 and 1300 have displayed the best functional properties. By differential thermal analysis, it has been shown that these samples have high thermal stability and do not decompose at temperatures of about 300A degrees C. Two representative samples of polyalkenyl succinimides in the composition of blended gasoline have been subjected to bench testing in a full-sized engine. A significant reduction in deposits on the engine intake valves has been noted upon testing the fuel in the presence of the synthesized samples with a concentration of 0.05 wt %.