The use of copolymers obtainable by - in a first reaction step copolymerizing at least one anhydride of an ethylenically unsaturated 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 optionally one or more further copolymerizable monomers other than monomers, and, selected from the group consisting of (Da) vinyl esters, (Db) vinyl ethers, (Dc) (meth)acrylic esters of alcohols having at least 5 carbon atoms, (Dd) allyl alcohols or ethers thereof, (De) N-vinyl compounds selected from the group consisting of vinyl compounds of heterocycles containing at least one nitrogen atom, N-vinylamides or N-vinyllactams, (Df) ethylenically unsaturated aromatics, (Dg) α,β-ethylenically unsaturated nitriles, (Dh) (meth)acrylamides and (Di) allylamines, followed by - in a second optional reaction step partly hydrolyzing the anhydride functionalities present in the copolymer obtained from, with the proviso that more than 90% of the anhydride functionalities present remain intact after reaction step, for removing and/or preventing deposits in the injection system of direct injection diesel and/or gasoline engines. - in a first reaction step copolymerizing at least one anhydride of an ethylenically unsaturated 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 optionally one or more further copolymerizable monomers other than monomers, and, selected from the group consisting of (Da) vinyl esters, (Db) vinyl ethers, (Dc) (meth)acrylic esters of alcohols having at least 5 carbon atoms, (Dd) allyl alcohols or ethers thereof, (De) N-vinyl compounds selected from the group consisting of vinyl compounds of heterocycles containing at least one nitrogen atom, N-vinylamides or N-vinyllactams, (Df) ethylenically unsaturated aromatics, (Dg) α,β-ethylenically unsaturated nitriles, (Dh) (meth)acrylamides and (Di) allylamines, followed by at least one anhydride of an ethylenically unsaturated 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 optionally one or more further copolymerizable monomers other than monomers, and, selected from the group consisting of (Da) vinyl esters, (Db) vinyl ethers, (Dc) (meth)acrylic esters of alcohols having at least 5 carbon atoms, (Dd) allyl alcohols or ethers thereof, (De) N-vinyl compounds selected from the group consisting of vinyl compounds of heterocycles containing at least one nitrogen atom, N-vinylamides or N-vinyllactams, (Df) ethylenically unsaturated aromatics, (Dg) α,β-ethylenically unsaturated nitriles, (Dh) (meth)acrylamides and (Di) allylamines, followed by (Da) vinyl esters, (Db) vinyl ethers, (Dc) (meth)acrylic esters of alcohols having at least 5 carbon atoms, (Dd) allyl alcohols or ethers thereof, (De) N-vinyl compounds selected from the group consisting of vinyl compounds of heterocycles containing at least one nitrogen atom, N-vinylamides or N-vinyllactams, (Df) ethylenically unsaturated aromatics, (Dg) α,β-ethylenically unsaturated nitriles, (Dh) (meth)acrylamides and (Di) allylamines, followed by - in a second optional reaction step partly hydrolyzing the anhydride functionalities present in the copolymer obtained from, with the proviso that more than 90% of the anhydride functionalities present remain intact after reaction step, for removing and/or preventing deposits in the injection system of direct injection diesel and/or gasoline engines.