What is the best model of brake fluid
Classification according to standard
In general, vehicle brake fluid is classified according to DOT. According to the American Petroleum Institute, brake fluid is divided into DOT3, DOT4, DOT5.1 three kinds.
1.DOT3, generally alcohol-ether type. The chemical composition of alcohol ethers is low polyethylene glycol or propylene glycol. ● Polyethylene glycol or propylene glycol has strong hydrophilic properties, so its water content will gradually increase during use or storage. Since the boiling point of brake oil will decrease with the increase of water content, its braking performance will also decrease. When you find that you need to press hard to stop, one possible reason is that the brake fluid contains too much water. Brake fluid is usually replaced every two years.
2.DOT4, generally an ester. Ester type is based on alcohol ether type with a large amount of borate ester added. Borates are formed by esterification of low polyethylene glycol or propylene glycol with boric acid. Borate has a higher boiling point than polyethylene glycol or propylene glycol, so the braking performance is better. Boric acid also has a strong moisture resistance, can decompose absorbed water, thereby slowing down the drop in boiling point caused by water absorption. Therefore, the ester type has better performance and higher price than the alcohol-ether type.
3.DOT5, generally silicone oil type. Refined from high cost silicone oil base oil, high temperature resistance water absorption ability is relatively strong, so can withstand relatively strong braking force. However, the silicon oil component will corrode the piston oil seal and brake tubing in the brake system, leading to brake fluid leakage, resulting in the failure of the brake system. However, DOT5.1 is generally used for professional racing or military purposes, and it is not sold on the market and can be ignored. In addition, there is also a brake night label DOT5, please do not be confused with DOT5.1, because the composition of this brake fluid is completely different from the general brake fluid, is completely hydrophilic, and ABS anti-lock braking system is completely incompatible. This label of brake fluid is only used for special purposes, so it is not sold on regular cars.
The main difference between DOT3 and DOT4 is the difference between dry and wet boiling points, known as the LDQUO equilibrium reflux boiling point and the LDQUO minimum wet boiling point. Our mandatory standard GB 12981-2003 "Motor vehicle brake fluid" also divided the brake fluid into DOT3 and DOT4 according to the boiling point of balanced reflux, the corresponding boiling point is & GE205 ℃, & GE at 230℃, if the boiling point of the brake fluid is too low, it is easy to vaporize in the system, resulting in air resistance, resulting in slow braking, or even brake failure.
Because the brake fluid base is alcohol, with hygroscopicity, with the extension of the use of time, the water content will gradually increase. DOT3 and DOT4 brake fluids can reach 3% water content after one year of use. When the water content in the brake fluid reaches a certain degree, the braking force will be weakened and the braking distance will be prolonged. So the general use of 2 years or 40 thousand kilometers to change the brake fluid. If the user used DOT3 brake fluid and wants to change to DOT4 brake fluid, the original brake fluid should be completely discharged. Different grades of brake fluid should not be used together.
For the replacement of brake oil, we must pay attention to the type of brake oil, such as DOT3 or DOT4, to avoid the reaction caused by the mixture of brake oil. The vehicle brake oil is best in line with the original factory standard oil, because the composition of different brands of brake oil is different, mixing is easy to cause chemical reaction corrosion pipeline and rubber parts, resulting in brake failure, it is recommended to use the original oil as far as possible.
