Factory-service automatic transmission fluids possess physical properties and performance features which differ substantially from the minimum Type A, Suffix A specification requirements. In some cases either the transmission life would be impaired by the use of a minimum Type A, Suffix A fluid, or desirable performance features would be deteriorated. These special factory requirements are discussed including low-temperature fluidity, frictional properties, clutch durability, antiwear characteristics, elastomer compatibility, and oxidative stability. The specialty factory fluids present questions concerning make-up oil additions and drain and refill practices. In spite of these, however, transmission manufacturers will continue to include the lubricant as an integral part of the total design. Thus service-station fluids should be carefully chosen to compromise manufacturers' conflicting recommendations.