what happens if you mix dot 3 and dot 4 brake fluid

According to the search results, DOT 3 and DOT 4 brake fluids can be mixed together without any harm to the braking system. However, it is important to note that DOT 4 brake fluid has a higher boiling point than DOT 3, which means that if DOT 4 fluid has taken on water and not changed for a long time, it can have an adverse effect on the braking system of the vehicle. Additionally, it is recommended to completely purge the system of the old DOT 3 fluid to take advantage of the DOT 4 features. It is also important to flush the brakes from time to time in order to get rid of the moisture in the system, as water can still contaminate both fluids and degrade their quality.