Why should DOT 5 fluid be avoided in anti-lock brake systems?

DOT 5 fluid should be avoided in anti-lock brake systems primarily because it is prone to aeration. This specific fluid, which is silica-based and not hygroscopic, can introduce air bubbles into the brake system under certain conditions. When these air bubbles form, they can lead to a spongy brake pedal feel and reduce the overall effectiveness of the braking system. In an anti-lock brake system (ABS), maintaining a precise hydraulic pressure is crucial for effective braking and stability control. If aeration occurs, the system may not function as intended, leading to compromised safety and performance.

Understanding the nature of DOT 5 fluid helps to highlight why other options were not the best reasons for its avoidance. For example, DOT 5 has a higher boiling point than some other brake fluids, which reduces the concern of boiling, and it does not inherently corrode brake components, as it is less aggressive than some other types. In addition, while DOT 5 can be mixed with other fluids, it is advisable to use the brake fluid that is specified for a particular system to maintain optimal performance and compatibility.