Question: what is the difference between brake fluid dot3 and dot4?
Answer: The basic difference between DOT3 and DOT4 is the boiling point. This is the temperature under which the fluid evaporates and also how prone to absorbing water it is. Both DOT3 and DOT4 are hygroscopic, meaning they absorb water. Due to its lower boiling point, DOT3 is more prone to water absorption.