J306_201902 Automotive Gear Lubricant Viscosity Classification

The SAE J306 Standard defines the limits for a classification of automotive gear lubricants in rheological terms. This standard is intended for use by equipment manufacturers in defining and recommending automotive gear, axle, and manual transmission lubricants. In 1998 and 2005, SAE created new viscosity grades in SAE J306 to better balance fuel economy and durability. In recent years, there has been greater focus on lower viscosity automotive gear lubricants to reduce churning power loss and improve operating efficiency. However, the current SAE J306 specification does not adequately define future low viscosity fluids. The newly revised SAE J306 standard addresses this shortcoming by tightening the broad kinematic viscosity window of SAE 80 grade as well as adding kinematic viscosity ranges for fluids below 7 cSt (currently SAE 80 lower limit). Ultimately, this standard will enable a more precise classification of automotive gear oil products as innovation continues in this space.