Brake fluid is a type of fluid used in the braking system to support the brake pedal. It consists of glycol ether or diethylene glycol to maintain a constant viscosity. The use of such chemicals allows the fluid to work even in extreme weather conditions. 

You can check brake fluid regularly by dipping the checking strips in them. For best performance, it needs to be sufficient in quality as well as quantity. Low levels of brake fluid can result in:

• Vibrations under braking
• Noisy brakes
• Pedal problems
• A burning smell
• Inefficient performance of the brake pads