If your brake fluid is at or above the “MIN” line, your brake fluid level is fine and you don't need to add any. If your fluid is below the “MIN” line, carefully pry the reservoir cap off, and then add brake fluid until the level is just under the “MAX” line. Do not overfill.
Correspondingly, can you use any brake fluid?
Check your vehicle's owner's manual to see if there are any specific instructions for the type of brake fluid you should use. Also, the cap usually states what kind of brake fluid is required. For the vast majority of vehicles, a standard glycol-based DOT 3 or DOT 4 brake fluid should be used.
What are the different types of brake fluid?
The three main types of brake fluid now available are DOT3, DOT4 and DOT5. DOT3 and DOT4 are glycol-based fluids, and DOT5 is silicon-based. The main difference is that DOT3 and DOT4 absorb water, while DOT5 doesn't. One of the important characteristics of brake fluid is its boiling point.
What happens if the brake fluid is low?
The second most common cause of low brake fluid is a leak. If you don't find out where it is leaking and fix the problem, then you could end up running the brake system dry. The end result is this: When you step on the brakes, the pedal will go all the way to the floor but it will not stop the car.