The present invention relates to functional fluid compositions containing antioxidants, and specifically stable compositions containing antioxidants with limited solubility in and/or limited compatibility with the functional fluids with which they are used. In particular the present invention deals with functional fluids used in internal combustion engines, such as engine oils, and antioxidants containing a phenolic or benzoic group, where the antioxidant is present in the functional fluid composition at levels that would otherwise cause the composition to be unstable and/or hazy.

A process is provided for preparing a salt of a hydroxy-substituted ester of phosphoric acid, comprising: (a) reacting a phosphate diester with an alkylene oxide, (b) reacting the product mixture of step (a) with a phosphating agent; and (c) reacting the product mixture of step (b) with an amine; wherein the phosphate diester is reacted with the alkylene oxide of step (a) in the substantial absence of a phosphate monoester. The product is useful as an antiwear agent.

A method of controlling wax deposition within a fluid, the method including admixing an additive composition with the fluid, wherein the additive composition includes one or more biosurfactants and one or more additional additives independently selected from (i) a sulfonic acid or salt thereof, (ii) a polymeric wax inhibitor and (iii) an alkoxylated alcohol and/or amine compound.