1.1 This classification is applicable to all petroleum-base fluid lubricants and to those nonpetroleum materials which may be readily blended to produce fluid lubricants of a desired viscosity, that is, lubricants for bearings, gears, compressor cylinders, hydraulic fluids, etc. 1.2 This classification is applicable to fluids ranging in kinematic viscosity from 2 to 3200 cSt (mm2/s) as measured at a reference temperature of 40°C. In the category of petroleumbase fluids, this covers the range from kerosine to heavy cylinder oils. 1.3 Fluids of either lesser or greater viscosity than the range described in 1.2 are, at present, seldom used as industrial lubricants. Should industrial practices change, then this system, based on a mathematical series of numbers, may be extended to retain its orderly progression.