Mixtures of carboxylic acids, their derivatives and hydroxyl-containing polymers and their use for improving the lubricating effect of oils

An additive for improving lubricating properties of fuel oils, comprising

• A) 10-95% by weight of at least one oil-soluble amphiphile of the formulae 1
• 7
• in which R1 is an alkyl, alkenyl, hydroxyalkyl or aromatic radical having 1 to 50 carbon atoms, X is NH, NR3, O or S, y is 1, 2, 3 or 4, R2 is hydrogen or an alkyl radical carrying hydroxyl groups and having 2 to 10 carbon atoms and R3 is an alkyl radical carrying nitrogen and/or hydroxyl groups and having 2 to 10 carbon atoms or a C1-C20-alkyl radical, or XR2 is NR41R42, in which R41 is a radical of the formula 3a
• —(R43—NR44)m—R—45 (3a)
• and R42 is a radical of the formula 3b
• —(R43—NR44)nR45 (3b),
• R43 is a C2- to C10-alkylene group, R44 is hydrogen, methyl, C2- to C20-alkyl, a radical of the formula 3c
• R1—CO— (3c)
• or an alkoxy radical, and R45 is hydrogen or a radical of the formula 3c, and m and n, in each case independently of one another, are an integer from 0 to 20, and
• B) 5-90% by weight of at least one copolymer which contains
• B1) from 0.5 to 15 mol % of structural units which are derived from olefinically unsaturated compounds which have at least one free hydroxyl group, and
• B2) from 85 to 99.5 mol % of structural units which are derived from ethylene, and, if required,
• B3) from 0 to 20 mol % of further structural units selected from the group consisting of (meth)acrylic acid, (meth)acrylates, vinyl esters, vinyl ethers and alkenes, with the proviso that the structural units stated under B3) differ from the structural units stated under B1) and B2),
• and the copolymer has an average molar mass Mw of from 500 to 100,000 g/mol and an OH number of from 5 to 300 mg KOH/g.