What Are the Specifications of Brake Fluid?
2 Answers
Brake fluid specifications include DOT3, DOT4, DOT5.1, etc. Characteristics of brake fluid: 1. Good viscosity-temperature performance with a low freezing point, ensuring excellent fluidity in low-temperature conditions; 2. High boiling point, preventing vapor lock in high-temperature conditions; 3. Minimal quality changes, avoiding corrosion and deterioration of metal and rubber. The method for replacing brake fluid is as follows: 1. Park the vehicle on a flat surface, turn off the engine, open the hood, and drain the fluid from the reservoir; 2. Use a funnel to fill the reservoir with new brake fluid; 3. Use a jack to lift the vehicle and start removing the tires from the rear wheels; 4. Remove the rubber dust cap on the brake caliper; 5. Use a wrench to loosen the bleeder screw, attach a rubber tube to it, and connect it to a drain bottle; 6. Press the brake pedal inside the vehicle while observing the draining process until the fluid level in the engine compartment reservoir reaches the lower limit.
I've been running an auto repair shop for years and have dealt with all kinds of brake fluid issues. The main specifications are DOT3, DOT4, DOT5, and DOT5.1. DOT3 has the lowest boiling point, around 205°C, suitable for older models, but it's highly hygroscopic and prone to problems in humid weather. DOT4 has a higher boiling point, exceeding 230°C, with broad compatibility, making it the choice for most modern vehicles. DOT5 is silicone-based, doesn't absorb water, but mixing it with DOT3 or DOT4 can corrode the system, so selection must be cautious. DOT5.1 has the highest boiling point, over 260°C, ideal for high-performance or electric vehicles. Choosing the wrong specification can lower the brake fluid's boiling point, causing bubbles to form during hard braking and leading to brake failure accidents. I help customers change their brake fluid every two years, strictly following the manual's recommendations—never making arbitrary changes. Also, if the fluid isn't changed for a long time, its performance degrades quickly due to moisture absorption, posing greater risks, especially in mountainous areas where temperature fluctuations are significant.
