What type of fluid is primarily used in automatic transmissions?

Automatic transmission fluid (ATF) is specifically formulated to meet the unique requirements of automatic transmission systems. It serves multiple critical functions, including lubrication of the moving parts inside the transmission, hydraulic fluid to enable the shifting of gears, and coolant to prevent overheating. The properties of ATF allow it to operate effectively under the specific temperature and pressure conditions found in an automatic transmission.

The formulation of ATF includes additives that help to improve performance, reduce wear, and prevent oxidation. This specialized design is essential, as using other types of fluids, such as engine oil, brake fluid, or coolant, would not provide the necessary lubrication, hydraulic function, or thermal stability required for the efficient and reliable operation of an automatic transmission.