Gear Oils and the Function of EP Additives

The multiple function of gear oils is described and the key properties required for satisfactory performance are reviewed. Special emphasis is placed on the EP properties and the corresponding additives necessary for the successful operation of gear oils. Analysis of the EP spectrum of properties allows for a better understanding of the chemistry of EP additives. It is pointed out that balancing among the EP components themselves and vis-a-vis the other performance additives is a critical part of a successful, universally effective, gear oil formulation.