A mixture contains(a) from 10 to 90% by weight of at least one imide of a copolymer based on an .alpha.-olefin and an ethylenically unsaturated dicarboxylic acid and a polyamine and(b) from 10 to 90% by weight of at least one reaction product of a poly(C.sub.2 -C.sub.20 -carboxylic acid) having a tertiary amino group with secondary aminesand is used as a paraffin dispersant in mineral oil middle distillates.