What are the main types of hydraulic fluid used in truck brake systems?

The correct choice identifies the main types of hydraulic fluid commonly utilized in truck brake systems, which include DOT 3, DOT 4, and DOT 5.

DOT 3 and DOT 4 fluids are glycol-ether-based and are known for their high boiling points, which is crucial for brake systems that can generate significant heat during operation. These fluids are hygroscopic, meaning they can absorb moisture from the air, which can lower their boiling points over time and potentially lead to brake failure if not maintained.

DOT 5, on the other hand, is a silicone-based fluid that is less likely to absorb moisture and can be advantageous in specific circumstances, such as when corrosion is a concern. However, it is important to note that DOT 5 fluids are not compatible with the earlier DOT fluids and should only be used in systems specifically designed for silicone fluids.

Understanding the specific types of hydraulic fluids and their properties is critical for maintaining the integrity and safety of truck brake systems. The other options, while they include some components that might be used in other applications, do not accurately reflect the primary fluids used specifically in truck brakes. For example, ATF (Automatic Transmission Fluid) is not suitable for brake systems, and mineral oil, water,