It was shown that for the polyisobutenes used in production of succinimide additives, the conditions of conducting the reaction that ensure the maximum yield of the final product are not a function of the a-isomer content in them. Alkenyl succinic anhydride is basically formed as a result of maleic anhydride reacting with isomers with the structure RCH3C=CH2 and RCH3C=CHCH3. Due to the reversibility of alkenylation of maleic anhydride, it is impossible to completely utilize the potential of polyisobutenes.