A method of improving the compatibility of a fuel additive composition comprising blending together the following components: a) a Mannich condensation product of (1) a high molecular weight alkyl-substituted hydroxyaromatic compound, (2) an amine having the formula:  wherein A is CH or nitrogen, R1, R2, R3 are independently hydrogen or lower alkyl of 1 to about 6 carbon atoms and each R2 and R3 is independently selected in each —CR2R3— unit, and x is an integer from 1 to about 6;  and (3) an aldehyde, wherein the respective molar ratio of reactants (1), (2), and (3) is 1:0.1-2:0.1-2; b) a hydrocarbyl-terminated poly(oxyalkylene) monool; c) a carboxylic acid as represented by the formula: R4(COOH)y  wherein R4 represents a hydrocarbyl group having about 2 to about 50 carbon atoms, and y represents an integer of 1 to about 4; and d) an anhydride selected from the group consisting of succinic, glutaric, phthalic, and alkyl anhydrides.