The dispersant is prepared by reacting an alkyl-substituted dicarboxylic acid compound selected from the group consisting of alkyl-substituted dicarboxylic acids, alkyl-substituted dicarboxylic acid anhydrides, and mixtures thereof, such as a polybutenyl succinic acid compound, e.g., polybutenyl succinic anhydride (PSA), and a basic salt of aminoguanidine, e.g. aminoguanidine bicarbonate (AGB), in