The reaction product resulting from the chemical reaction of an alkyl phenol with an acid or an anhydride selected from the group consisting of a saturated dicarboxylic acid, an unsaturated dicarboxylic acid, an anhydride of a saturated dicarboxylic acid, an anhydride of an unsaturated dicarboxylic acid, and combinations thereof, has been discovered to improve the properties of various fluids. In a non-limiting example, the reaction products may have an acid number from about 0 to about 50 that may improve the lubricity and/or corrosion of fuels and lubricants, such as hydrocarbon fuels and lubricants, when added thereto.