(EN) The invention relates to a polymer comprising 50-100% by weight, with regard to the weight of the polymers, of repeating units, which are derived from one or more ethylenically unsaturated ester compounds of formula (I), in which R represents hydrogen or methyl; R1 represents a linear or unbranched alkyl radical with 7 to 30 carbon atoms, and; R2 and R3 independently represent hydrogen or a group of formula —COOR′, wherein R′ represents hydrogen or an alkyl group with 7 to 30 carbon atoms. The polymer is a star polymer with 3 to 21 arms and at least 3 of the arms consist of at least 40% by weight, with regard to the weight of the arms, of repeating units, which are derived from one or more ethylenically unsaturated ester compounds of formula (I), in which R1 represents a linear or unbranched alkyl radical with 7 to 30 carbon atoms, and; R2 and R3 independently represent hydrogen or a group of formula —COOR′, wherein R′ represents hydrogen or an alkyl group with 7 to 30 carbon atoms. The invention also relates to oil formulations comprising the inventive polymers. The inventive polymers having a high thickening action can be used, in particular, as viscosity modifiers, pour point depressants, dispersing agents and/or friction modifiers.