SAE Axle and Manual Transmission Gear Oil Viscosity Classification - automotive gear oil classification system developed by the Society of Automotive Engineers (SAE). The SAE 70W, 75W, 80W, and 85W viscosity grades are determined by the maximum cold temperature at which a viscosity of 150,000 cp is attained. For the SAE 90, 140, and 250 grades, minimum and maximum viscosities at 100°C establish the grade designations. Gear oil SAE viscosity grades should not be confused with engine oil SAE viscosity grades. See SAE engine oil viscosity classification.