Brake fluid is a hydraulic fluid that helps transfer force from the brake pedal to the brakes themselves. When you press the brake pedal, brake fluid is forced through a series of hoses and valves to the brakes, where it applies pressure to the brake pads or shoes, causing them to clamp down on the rotors or drums. Brake fluid is vital to the proper operation of your brakes, and it is important to keep it at the correct level. If the level gets too low, there may not be enough fluid to transfer sufficient force to the brakes, and your brakes may not work properly. The amount of brake fluid you need will depend on the size of your vehicle's braking system. Most vehicles have a reservoir that holds about a quart (0.95 l) of fluid. However, some larger vehicles may have a reservoir that holds up to a gallon (3.8 l) or more. It is important to check your brake fluid level