In terms of high temperature performance, the equilibrium reflux boiling point of DOT4 is 230 C, and the equilibrium reflux boiling point of DOT3 is 205 C. Vehicles using DOT4 brake fluid have better braking stability more frequently.

The liquid medium which transmits braking pressure in the hydraulic braking system of brake fluid vehicle is used in the vehicle with hydraulic braking system. The performance requirements of brake fluid are: good viscous temperature, low solidification point, good low temperature fluidity; high boiling point, high temperature gas resistance; quality changes during use, and causes corrosion and deterioration of metal and rubber parts.

(1) There should be a higher boiling point. In modern automobiles, braking frequently occurs, and the temperature of brake drum (disc) keeps rising. If the brake fluid with lower boiling point is used, air resistance often occurs in the pipeline, which leads to braking failure. Therefore, the evaporation of brake fluid is low and it is easy to vaporize at high temperature.

(2) Suitable high temperature viscosity and good low temperature fluidity. Brake fluid can transfer pressure under various conditions, and make the moving parts in the transmission mechanism get certain lubrication.

(3) It has the properties of anti-oxidation, anti-corrosion and anti-rust. Long-term contact between brake fluid and metal should result in colloidal and corrosive substances, or discoloration due to rust, or even pitting.

(4) Low hygroscopicity, good water solubility and less boiling point drop. Even if water enters the brake fluid, it can form particles and mix with the brake fluid evenly, resulting in separation and precipitation.

(5) Good adaptability to rubber. Brake fluid should swell rubber parts, otherwise it will lose its proper sealing effect, so brake fluid has good adaptability to rubber parts.

In spring and summer, it is based on the water solubility of brake fluid, reminding everyone to pay attention to check the brake fluid situation in daily vehicles, to avoid excessive moisture integration, affecting the braking effect of vehicles.