Why carmakers switched to DOT 5.1 brake fluid

DOT 5.1 is the newest brake fluid and provides some big benefits to late model vehicles

DOT 5.1 brake fluid is a lower viscosity than DOT 3 or DOT 4. It also has a higher boiling point. So it works better in situations where rapid and pulsed braking is required. Late model cars and trucks have advanced driver assistance systems (ADAS) that include; automatic emergency braking, accident avoidance, adaptive cruise control, stability and traction control and lane change warning system. Each of these systems can activate the brakes to avoid a collision and that can involve rapid and pulsed braking.

DOT 5.1 is not the same as DOT 5!

Many people think that DOT 5.1 brake fluid is just another version of DOT 5 silicone fluid. It’s NOT, and it’s not compatible with DOT 5. Do not mix DOT 5 and DOT 5.1.

How DOT 5.1 brake fluid is different than DOT 3 and DOT 4

Click on the image to learn more about DOT 5.1

It’s all about brake fluid boiling points. DOT 5.1 has a higher boiling point than DOT 3 or DOT 4. Brake fluid boiling points are rated on two scales; dry and wet.

DOT 5.1 brake fluid is available in either clear, yellow or blue. Unlike DOT 5 which can’t be mixed with DOT or DOT 4, DOT 5.1 is compatible with DOT 3 and DOT 4 fluid and can be used in conventional applications. DOT 5.1 has one huge advantage over the other brake fluids as it has much higher dry (500 °F) and wet boiling points (356 °F). This makes DOT 5.1 the ideal choice for use in high-performance vehicles and heavy-duty applications.

Dry boiling point

Dry boiling point is measured with the fluid containing 0% water by volume.

Wet boiling point

Wet boiling point is measured with the fluid containing 3.7% water by volume

Brake fluid color

Fresh DOT 5 brake fluid is purple. DOT 5.1 can be clear, yellow or blue.

Over time, all glycol based brake fluids darken. But color alone is NOT an indication of brake fluid condition. What causes the discoloration? Moisture and normal rubber degradation.

The ONLY way to determine brake fluid condition is with test strips and a moisture meter or refractometer.

What is LMA fluid?

Low Moisture Activity brake fluid is designed to accumulate less moisture, thus resulting in a higher boiling point.

©, 2023 Rick Muscoplat