Hypoid gear oil is a type of gear oil that is formulated with extreme-pressure (EP) additives to protect and operate effectively with hypoid gears. Hypoid gears are a type of spiral bevel gear found in axle differentials and used to transfer power to the axle shafts from the driveline. They engage the pinion under the centerline of the ring gear, which drops the driveshaft away from the vehicle’s underside. Hypoid gearsets are fairly similar to spiral bevel gear setup, with the difference that hypoid gears have an axis that is non-intersecting and not parallel. This unique alignment of the gears requires a special lubricant that can stand up to the pressures and temperatures in the gearbox. Hypoid gear oil is recommended for use in automotive and heavy-duty truck rear differentials where high torque and load handling is needed. It is also used in steering boxes, steering swivels, and other differentials. The importance of using hypoid gear oil is that it can extend the life of the hypoid gearsets.