This SAE Standard defines the limits for a classification of automotive gear lubricants in rheological terms only. Other lubricant characteristics are not considered.
Two new viscosity grades were added to the viscosity classification as part of the January 2005 update. The new grades are SAE 110 (100 °C viscosity between 18.5 and 24.0 cSt) and SAE 190 (100 °C viscosity between 32.5 and 41.0 cST). The need for the two additional grades centered on the wide variation in kinematic viscosity possible within the prior version of J306 for SAE 90 and the SAE 140 grades. The effect of such a wide range of kinematic viscosities could result in an axle being serviced with a lubricant that had a viscosity significantly lower or higher than the axle lubricant that the axle had been validated with, even though the same viscosity grade had been employed. OEMs may have been forced to specify a higher viscosity grade than what they may actually desire, because the wide range of kinematic viscosities of the next lower grade could result in customers using a lubricant having too low of a kinematic viscosity. For example: An OEM would like to recommend a lubricant having a 100 °C viscosity of 19.5 cSt, which according to the prior version of J306 requirements would be SAE 90. However, if the OEM had recommended a SAE 90 the actual viscosity could be as low as 13.5 cSt, which may be lower than the OEM is comfortable with. Thus, the OEM recommended a SAE 140, which ensures that the 100 °C viscosity is never lower than the desired 19.5. Unfortunately, that also means that the viscosity could be as high as 41.0 cSt. Under the new limits the OEM could recommend a SAE 110 which would meet the 19.5 cSt requirement and the axle would not be serviced with anything higher in viscosity than 31 cSt.
An additional change to J306 was the inclusion for the use of ASTM D 3244 for resolving any disputes between laboratories as to whether a product conforms with any specification in Table 1.
The test designation for the KRL Shear Stability Test was also updated to the current designation.