The use of a complex ester obtainable by esterification reaction between aliphatic linear or branched C2- to C12-dicarboxylic acids, aliphatic linear or branched polyhydroxy alcohols with 3 to 6 hydroxyl groups, and, as chain stopping agents, aliphatic linear or branched C1- to C30-monocarboxylic acids or aliphatic linear or branched monobasic Ci- to C30-alcohols, as an additive in a fuel.