Demulsifier composition for automatic transmission fluids

An automatic transmission fluid comprising a formulated automatic transmission fluid containing a demulsifier additive, said additive providing effective demulsification at concentrations of 30 to 50 parts per million, the demulsifier consisting essentially of two components:

• (a) 50 to 75 weight percent of a solution in aromatic hydrocarbon solvent of an oil soluble isopentylphenol-formaldehyde resin having a degree of polymerization of 5-10, the resin being alkoxylated with 1 to 5 moles of ethylene oxide or propylene oxide and acylated by reaction with acetic acid or propionic acid, the solution having a concentration of 35 to 50 weight percent of said resin;
• and
• (b) 50 to 25 weight percent of a 40 to 50 weight percent solution in aromatic hydrocarbon solvent of an oil soluble amylphenolformaldehyde resin having a degree of polymerization of 5-10 which has been alkoxylated with a propylene oxide-ethylene oxide mixture, the mixture containing 60-70 weight percent of propylene oxide, the weight ratio of resin to said mixture being 1 to 2.5.