The effects of automatic transmission fluid additives on the friction characteristics of a mineral oil are presented. Some common viscosity-index improvers, chain-breaking oxidation inhibitors, and ashless dispersants have little or no effect on the friction characteristics of the mineral oil. Conversely, some metal-organic dispersants as well as a zinc 0,0′-dialkylphosphorodithioate oxidation inhibitor alter the friction characteristics of the mineral oil. The results indicate that some of the additives are multifunctional and will render the friction characteristics of the mineral oil satisfactory. Relationships between molecular structure of the additives and friction characteristics are discussed, but general conclusions are not formulated.Presented as an American Society of Lubrication Engineers Paper at the Lubrication Conference held in Minneapolis. Minnesota, October 18–20, 1966.