What fluid is typically used in an automatic transmission?

Automatic transmission fluid (ATF) is specifically designed for use in automatic transmissions. It serves multiple critical functions, including lubricating the moving parts of the transmission, providing hydraulic pressure to engage the clutches and bands within the transmission, and facilitating proper heat dissipation. The unique formulation of ATF includes additives that enhance its performance, such as those that reduce friction, prevent oxidation, and protect against wear.

Engine oil is formulated for the lubrication and cooling of the engine, while hydraulic fluid is used in systems like power steering or brake systems but does not have the specific properties required for an automatic transmission. Brake fluid is used exclusively in braking systems and is not compatible with the materials used in transmissions. Therefore, ATF is the correct choice as it is specifically tailored to meet the requirements and demands of automatic transmissions, ensuring their effective operation and longevity.