Corrosion inhibitors for fuels and lubricants

A corrosion inhibitor, comprising a reaction product that is essentially free of acid groups and is obtained by reacting:

• a polyisobutene (A), having a number-average molecular weight Mn of 200 to 10,000, with
• a maleic acid derivative (B) comprising an anhydride,
• in a stoichiometric ratio of more than one equivalent of (B) per a total of terminal α- and β-double bonds, determined by 13C NMR, in (A),
• where a bismaleation level, calculated as 100%×[(wt-% (BM PIBSA)/(wt-% (BM PIBSA)+wt-% (PIBSA))], wherein PIBSA represents monomaleated polyisobutene and BM PIBSA represents polymaleated polyisobutene, is 15% to 40%,
• with the proviso that more than 90% of the anhydride groups present in (B) are conserved in the reaction product.