Abstract: For many different reasons, differential temperatures have increased to levels that may significantly shorten the life of the fluid and threaten the durability of the differential. Automotive and lubricant manufacturers are faced with a serious challenge. They must develop differential fluids with the ability to withstand oxidation with its potentially highly adverse mulitple effects. These effects include viscosity increase, deposit formation and oxidative decomposition of the fluid's functionality. Such an effort requires an effective bench screening test because of the time, costs, and limited repeatability associated with fleet tests of differential fluid performance. With this evident challenge, this paper reports development of a test protocol called the VDOT -- an acronym for Viscosity, Deposit, and Oxidation Test. This new test measures viscosity and oxidation change as well as deposit formation tendency of gear oils as a means of understanding the relationship between differential temperatures and fluid degradation.