Automatic transmissions in diesel-run vehicles have extremely complex compositions when compared to manual transmissions and, as such, require different fluids to transmit power and provide lubrication.

Automatic Transmission Fluids are typically specially formulated versions of hydraulic oil. Hydraulics, which do not have a place in a manual transmission (which are simply amalgamations of manually shifted gears), are the means by which an automatic transmission controls the various clutches and bands that modify speed and power output. The oil pump draws incompressible transmission fluid from an oil reservoir and pressurizes it which inputs the necessary force for transmission operation. The hydraulic and lubricating oil known as Automatic Transmission Fluid, or ATF, prevents corrosion of expensive transmission parts and provides a hydraulic medium to transmit power: as such, it is important to invest in a high quality fluid to ensure long oil life and high performance.

ATFs - especially those that are fully synthetic - at work in heavy duty applications are suited to handle the lubrication and power output demands of transmissions operating under severe service conditions or in large vehicles that may employ a powershift transmission. Also, many of these fluids function exceptionally well in hydraulic industrial and mobile equipment.