Ethylene-based copolymers suitable as viscosity improvers for petroleum distillates of a) 50 to 94 wt. % ethylene; b) 3 to 30 wt. % one or more vinyl esters of C2-C6 monocarboxylic acids; c) 3 to 20 wt. % one or more aminoalkylene acrylates of general formula (I) in which R1 is hydrogen or methyl, the radicals R?2 and R3¿ may be the same or different and stand for hydrogen or a C¿1?-C6 alkyl radical and A?1¿ is a straight-chained or branched C¿2?-C10 alkylene radical; and d) 0 to 10 wt. % one or more monomers which can be copolymerised with monomers a) to c), in which such copolymers are excluded in which monomer b) is vinyl acetate and have a number average molecular weight of 5000 to 50000; or of a') 50 to 95.5 wt. % ethylene; b') 4 to 30 wt. % one or more vinyl esters of C2-C6 monocarboxylic acids; c') 0.5 to 20 wt. % one or more vinyl imidazoles of general formula (II) in which the radicals R?4, R5 and R6¿ may be the same or different and are hydrogen or a C¿1?-C6 alkyl radical, or 0.5 to 20 wt. % one or more aminoalkyl vinyl ethers of general formula (III) in which the substituents are: R?7, R8: C¿1-C6 alkyl; R?9, R10, R11¿: hydrogen or C¿1?-C6 alkyl; A?2: C¿2-C6 alkylene; and d') 0 to 10 wt. % one or more monomers which can be copolymerised with monomers a') to c'). The invention also relates to the use of these copolymers as viscosity improvers for petroleum middle distillates and to pretroleum distillates containing them.