This International Standard specifies the requirements of lubricating engine oils (hereinafter referred to as “four-stroke engine oils”) to be used in four-stroke cycle spark ignition gasoline engines employing a common sump containing the lubricating oil for both the engine and associated drivetrain (transmission, clutch, starter) of motorcycles, motor scooters, all-terrain vehicles (ATVs) and related equipment. Classification of four-stroke engine oils is defined in ISO 6743-15 [1]. Among all of the categories covered by ISO 6743-15, this International Standard includes categories EMA and EMB. This International Standard specifies the performance classification of four-stroke cycle gasoline engine oils based on physical and chemical properties, and three friction performance indices, which are derived from the frictional properties of the lubricant, according to the JASO T904 test procedure1). NOTE For the purposes of this International Standard, the term “% (m/m)” is used to represent the mass fraction.