Can I mix DOT 3, DOT 4, and DOT 5 brake fluids? DOT 5.1 has the same dry and wet boiling point as DOT 5 and offers the same level of performance. DOT 5.1 Brake FluidĭOT 5.1 is a reformulated blend of DOT 5 brake fluid and is compatible with DOT 3 and DOT 4 braking systems despite being silicone-based. With such impressive numbers, DOT 5 is better resistant to rust and corrosion and lasts longer than DOT 3 or DOT 4. DOT 5 brake fluid has a dry boiling point of 260☌ and a wet boiling point of 180☌. Unlike poly-glycol-based DOT 3 and DOT 4 brake fluid, DOT 5 is silicone-based, does not absorb moisture, and has a more watery consistency. Since DOT 4 has a higher dry and wet boiling point than DOT 3, it offers better resistance to extreme heat and moisture to deliver reliable stopping power. DOT 4 Brake FluidĭOT 4 brake fluid has a dry boiling point of 230☌ and a wet boiling point of 155☌. The dry boiling point refers to fresh brake fluid, while the wet boiling point is when the brake fluid has absorbed moisture after repeated use. It has a dry boiling point of 205 ☌ and a wet boiling point of 140☌. Generally, brake fluid with a higher boiling point will last longer than others with a lower number. All brake fluids have a DOT (Department of Transport) rating, and the numbers relate to the fluid’s dry and wet boiling points. What’s the difference between DOT 3, DOT 4, and DOT 5 brake fluid?Ĭar owners need to choose between DOT 3, DOT 4, and DOT 5 when buying a fresh bottle of brake fluid. It’s the reason why periodically flushing and changing the brake fluid is of utmost importance. And when the brake fluid boils, moisture will turn to vapor inside the brake lines, giving your brake pedal a softer and spongier feel, effectively losing the ability to compress the calipers and stop your vehicle. For starters, absorbing water or moisture is good in preventing rust and deterioration of braking components.īut then again, too much water in the brake fluid significantly lowers the freezing or boiling point of the liquid. Brake fluid is hygroscopic by design, meaning it absorbs moisture faster than any other fluid, and this can be a good and bad thing. Water vapor intrudes your car’s brakes via microscopic pores in the hydraulic brake lines and the build-up of air in the reservoir. How does brake fluid affect braking performance?

Furthermore, the brake fluid lubricates the rubber and metal components in the calipers and master cylinder to prevent rust and corrosion. In effect, the brake fluid transfers the force applied to the brake pedal to the brake calipers.Īnd since the brakes are operating in a high-friction and high-stress environment, the brake fluid needs to perform flawlessly at extreme temperatures and high-pressure scenarios. Upon pressing the brake pedal, the brake fluid pushes the pistons in the caliper to grip the brake rotors, the reason why your car pulls to a stop or reduces speed when applying brake pedal pressure. Modern cars need either DOT 3, DOT 4, or DOT 5 brake fluid, but what’s the difference between each, and what is best for your vehicle? What is brake fluid?īrake fluid is a hydraulic fluid utilized by the braking system in your ride. However, buying a fresh bottle of brake fluid is not as simple as it sounds.

If you regularly change the engine oil to keep the engine humming, it’s also a good idea to change the brake fluid to keep those anchors in tip-top shape. The brake fluid is probably one of the most overlooked maintenance items in your ride. What’s the difference between brake fluids?

Dot 3 brake fluid comparison