What type of fluid is typically used in automatic transmissions?

Automatic Transmission Fluid (ATF) is specifically formulated for use in automatic transmissions, making it the appropriate choice for this question. ATF is designed to provide the necessary lubrication, cooling, and hydraulic pressure required for the intricate components of an automatic transmission to function effectively.

This fluid has the right balance of additives that enhance its performance, including friction modifiers for smooth gear shifts, detergents to keep the transmission clean, and anti-wear agents to protect the internal surfaces from damage. Its unique properties enable it to withstand high temperatures and pressures, which are common in an automatic transmission's operating environment.

In contrast, engine oil is intended for the lubrication of engine components and does not offer the specific characteristics needed for automatic transmission systems. Hydraulic brake fluid is designed for braking systems and lacks the properties necessary for lubrication and transmission function. Water-based fluid would not provide the required viscosity and chemical stability needed for transmission operation and could cause significant damage. Thus, ATF is the industry standard for automatic transmission applications.