Can DOT3 brake fluid not be replaced with DOT4?

[JakeLee]

DOT3 cannot be replaced with DOT4 brake fluid. DOT3 and DOT4 are different models with varying compositions and boiling points, which can cause damage to the engine. DOT3 is composed of alcohols and ethers, while DOT4 is mainly formulated with polyglycol borate as the primary raw material. The alcohol and ether materials used in DOT3 do not meet the specifications required for DOT4. Characteristics of brake fluid include: 1. A very low freezing point, ensuring good fluidity at low temperatures; 2. A high boiling point, preventing vapor lock at high temperatures; 3. Minimal quality changes, avoiding corrosion of metals and rubber. The steps for replacing brake fluid are: 1. Position the vehicle over a pit or lift it with a jack; 2. Clean the drain port, remove the dust cap, unscrew the drain port screw, repeatedly press the brake pedal, and tighten the drain port screw once the fluid runs clear; 3. Add new brake fluid.