Question: what is the difference between dot 3 and 4 brake fluid?
Answer: While DOT 4 is compatible with DOT 3, it does not work the other way around. As we have just mentioned, the most obvious difference between DOT 3 and DOT 4 brake fluid is the boiling point, which is the temperature that the fluid evaporates. ... But since it has a lower boiling point, DOT 3 tends to absorb water.