Which type of brake fluid has the lowest boiling point?

The type of brake fluid with the lowest boiling point is indeed DOT 3. DOT 3 brake fluid is hygroscopic, meaning it absorbs moisture from the air over time, which can lead to a decrease in its boiling point as it becomes contaminated with water. The typical boiling point for DOT 3 fluids in a new, uncontaminated state is around 205 degrees Celsius (401 degrees Fahrenheit).

In comparison, DOT 4 and DOT 5.1 have higher boiling points, with DOT 4 typically ranging from 230 degrees Celsius (446 degrees Fahrenheit) to 260 degrees Celsius (500 degrees Fahrenheit), and DOT 5.1 being even higher, making them more suitable for vehicles that require higher performance braking systems, especially in severe conditions. DOT 5, on the other hand, is silicone-based and does not absorb water, but it has distinct properties that make it incompatible with systems designed for glycol-based fluids such as DOT 3 and DOT 4.

Understanding the boiling points of different brake fluids is important for ensuring optimal braking performance and safety, especially in high-stress scenarios where overheating can lead to brake failure. The knowledge of these characteristics helps automotive professionals make better recommendations for brake system maintenance and fluid selection.