Abstract: A bifunctional anti-settling and dispersant additive for middle distillates from 150-450.degree. C. petroleum fractions, characterized in that consists of at least one modified copolymer with a weight-average molecular weight of 500-5000 prepared as follows: in a first step, a first carboxylic acid is copolymerized with an alkylated ester of a second carboxylic acid which is the same as or different from the first, and in a second step, the carboxylic groupings of the resulting copolymer re amidified at a temperature of 100-200.degree. C. ##STR1## wherein n and m are from 1 to 8, and R and R' are preferably alkyl groupings.