A sulphur-free polymer comprising structural units of formula (I) and structural units of formula (II): wherein R1 represents a C8 to C22 alkyl group, preferably a C12 to C16 alkyl group; wherein R2 is hydrogen or methyl; wherein R3 represents —R5(OR6)nOR7; wherein R5 and R6 may be the same or different and independently represent a linear or branched C1 to C8 alkylene group; wherein n is an integer from 1 to 20; wherein R7 represents a C1 to C4 alkyl group; wherein R4 is hydrogen or methyl; and wherein the molar ratio of structural units (I):structural units (II) in the polymer is in the range from 100:1 to 2:1. The polymers improve the low-temperature properties of fuel oils from petroleum sources, those from vegetable or animal sources, and mixtures of these fuel oils.