Brake fluid is one of the most important fluids in your car. It helps to transfer the force from your foot on the pedal to the brakes themselves. Over time, brake fluid can become contaminated and will need to be flushed out. Depending on how often you drive and what kind of conditions you typically encounter, your brake fluid could last anywhere from 20,000 to 50,000 miles. However, it’s always best to check your owner’s manual or with a mechanic to be sure.