Abstract: Antifoam compositions for functional fluids contain antifoam agents comprising perfluoropolyether compounds (PFPE). An automatic transmission fluid is provided containing the antifoam composition in a lubricating base oil, along with conventional additives such as antiwear agents. Automobile transmissions are provided that contain an automatic transmission fluid containing the new antifoam compositions. In a further embodiment, methods are provided for reducing foam in an engine oil or unwanted noise in an automobile transmission during operation, comprising lubricating the engine or transmission with a lubricating fluid containing the antifoam compositions of the invention.