Use of nitrogen compounds quaternised with alkylene oxide and hydrocarbyl-substituted polycarboxylic acid as additives in fuels and lubricants

A method for preparing a gasoline fuel composition or diesel fuel composition, comprising:

• adding to a gasoline or diesel fuel, a salt or a purified form thereof of a hydrocarbyl-substituted polycarboxylic acid and a hydrocarbyl epoxide quaternized nitrogen compound obtained by reaction of an alkylamine of formula (3) with a quaternizing agent of formula (4) to obtain a quaternized nitrogen compound of formula (2a), formula (2b) or a mixture thereof according to Eq. (I);
• wherein the reaction with the quaternizing agent is in the presence of a free hydrocarbyl-substituted polycarboxylic acid of formula (1);
• wherein
• radicals R2, R3 and R4 are each independently a straight-chain or branched, C1-C7-alkyl residue,
• R5 is H or an aliphatic or aromatic radical comprising 1 to 10 carbon atoms,
• R1 is a long-chain hydrocarbyl having a number-average molecular weight (Mn) of 85 to 20,000;
• and
• R is H or a radical CH2CH(R5)OH or a radical CH(R5) CH2OH.