The use of copolymers obtainable by - in a first reaction step copolymerizing at least one ethylenically unsaturated mono- or dicarboxylic acid or derivatives thereof, preferably a dicarboxylic acid or derivatives thereof, more preferably the anhydride of a dicarboxylic acid, at least one α-olefin having from at least 12 up to and including 30 carbon atoms, optionally at least one further aliphatic or cycloaliphatic olefin which has at least 4 carbon atoms and is different than and at least one (meth)acrylic ester of alcohols having at least 5 carbon atoms, where component used is maleic anhydride, where the molar incorporation ratio in the copolymer of /( and) (in total) is from 10:1 to 1:10 and where the proportion of one or more of the (meth)acrylic esters based on the amount of monomers, and optionally (in total) is 5 to 200 mol%, followed by - in a second reaction step partly or fully hydrolyzing the anhydride functionalities present in the copolymer obtained from and/or partly hydrolyzing carboxylic ester functionalities present in the copolymer obtained from, where at least 10% of the anhydride functionalities are hydrolyzed, and where the copolymer obtained from reaction step has a number-average molecular weight Mn of 0.5 to 10 kDa, for removing and/or preventing deposits in the fuel system and/or injection system of direct injection diesel and/or gasoline engines. - in a first reaction step copolymerizing at least one ethylenically unsaturated mono- or dicarboxylic acid or derivatives thereof, preferably a dicarboxylic acid or derivatives thereof, more preferably the anhydride of a dicarboxylic acid, at least one α-olefin having from at least 12 up to and including 30 carbon atoms, optionally at least one further aliphatic or cycloaliphatic olefin which has at least 4 carbon atoms and is different than and at least one (meth)acrylic ester of alcohols having at least 5 carbon atoms, where component used is maleic anhydride, where the molar incorporation ratio in the copolymer of /( and) (in total) is from 10:1 to 1:10 and where the proportion of one or more of the (meth)acrylic esters based on the amount of monomers, and optionally (in total) is 5 to 200 mol%, followed by at least one ethylenically unsaturated mono- or dicarboxylic acid or derivatives thereof, preferably a dicarboxylic acid or derivatives thereof, more preferably the anhydride of a dicarboxylic acid, at least one α-olefin having from at least 12 up to and including 30 carbon atoms, optionally at least one further aliphatic or cycloaliphatic olefin which has at least 4 carbon atoms and is different than and at least one (meth)acrylic ester of alcohols having at least 5 carbon atoms, where component used is maleic anhydride, where the molar incorporation ratio in the copolymer of /( and) (in total) is from 10:1 to 1:10 and where the proportion of one or more of the (meth)acrylic esters based on the amount of monomers, and optionally (in total) is 5 to 200 mol%, followed by where component used is maleic anhydride, where the molar incorporation ratio in the copolymer of /( and) (in total) is from 10:1 to 1:10 and where the proportion of one or more of the (meth)acrylic esters based on the amount of monomers, and optionally (in total) is 5 to 200 mol%, followed by - in a second reaction step partly or fully hydrolyzing the anhydride functionalities present in the copolymer obtained from and/or partly hydrolyzing carboxylic ester functionalities present in the copolymer obtained from, where at least 10% of the anhydride functionalities are hydrolyzed, and where the copolymer obtained from reaction step has a number-average molecular weight Mn of 0.5 to 10 kDa, for removing and/or preventing deposits in the fuel system and/or injection system of direct injection diesel and/or gasoline engines. where the copolymer obtained from reaction step has a number-average molecular weight Mn of 0.5 to 10 kDa, for removing and/or preventing deposits in the fuel system and/or injection system of direct injection diesel and/or gasoline engines.