Abstract: Disclosed is a composition resulting, in a first stage, from the reaction of at least one alkenyl or polyalkenylsuccinic acid or anhydride on at least one 1-(2-hydroxyethyl)-imidazoline substituted in the 2-position by a linear or branched alkyl or alkenyl radical, with 1 to 25 atoms of carbon in an imidazoline to succinic derivative molar ratio of 0.1:1 to 0.9:1 with the removal of at least 0.15 mole of water per mole of imidazoline, and then, in a second stage, from the reaction of the product obtained in the first stage on at least one polyamine in an amount representing at least 0.1 mole per mole of the succinic derivative utilized in the first stage.Also disclosed are methods for the utilization of these compositions as multifunction additives in engine fuels having as a base hydrocarbons or a mixture of hydrocarbons and at least one oxygen compound selected from the group constituted by alcohols and ethers.