What is the difference between brake fluid T3 and brake fluid T4?
3 Answers
The difference between brake fluid T3 and brake fluid T4 lies in their boiling points: the boiling point of brake fluid T3 is 205 degrees Celsius, while that of brake fluid T4 is 230 degrees Celsius. Brake fluid T4 is of a higher grade than brake fluid T3. The temperature in the braking system can get very high, and moisture can gradually accumulate in the brake fluid. High temperatures can cause this moisture to turn into gas, leading to poor braking performance, which is why it is necessary to replace the brake fluid regularly. Brake fluid is the liquid medium that transmits braking pressure in hydraulic braking systems, used in vehicles equipped with hydraulic braking systems. Within the braking system, it serves as a force transmission medium. Since liquids are incompressible, the pressure output from the master cylinder is directly transmitted to the wheel cylinders through the brake fluid.
I've been driving for almost 20 years and always do my own maintenance. The biggest difference between DOT 3 and DOT 4 brake fluid lies in their high-temperature resistance. DOT 4 has a dry boiling point around 230°C, while DOT 3 barely exceeds 200°C. You might not notice the difference during city driving, but when going downhill continuously on mountain roads, DOT 4 performs significantly better at resisting vapor lock that causes brake fade. Another practical difference is moisture absorption - DOT 4 contains borate esters in its formula to better encapsulate water and reduce corrosion, which I clearly observed when changing brake pads last week after opening the reservoir. The shop mechanic mentioned most modern cars come with DOT 4 as standard now, though older vehicles can still use DOT 3. The key is to avoid mixing them to prevent sediment buildup that could clog the lines.
Our car enthusiasts group just discussed this last week. Brake fluids T3 and T4 are completely different in formulation design. T3 uses glycol ether as base fluid – it absorbs moisture like a sponge but degrades easily. T4 incorporates borate esters, acting like an antioxidant shield for the fluid, not only increasing boiling point by over 15% but also locking water molecules more securely. Here's a concrete data point: after two years of use, T3 typically contains about 3% water content while T4 only reaches 1.5%. This means the corrosion rate of metal brake lines is halved, and piston seals are less prone to deformation or leakage. For routine maintenance, we strongly recommend prioritizing T4, especially for vehicles with modified braking systems – its high-temperature stability is significantly superior.
