Changing your brake fluid is one of the more approachable DIY brake jobs - it needs no rotor removal, just patience and care. Since old fluid quietly ruins pedal feel and corrodes parts, doing it on schedule is worthwhile. Here is the DIY overview.
Why and when to do it
Brake fluid absorbs moisture over time, lowering its boiling point and corroding the system - see how often to change brake fluid. Most makers call for it every 2-3 years. A DIY flush replaces the old fluid with fresh, restoring a firm pedal and protecting the ABS unit and calipers.
What you need
The correct fluid type for your car from a sealed container - see DOT 3 vs DOT 4 - a wrench or bleeder wrench, clear tubing and a catch bottle, and ideally a helper or a one-person bleeder kit. Never use fluid from an old opened bottle; it has already absorbed moisture.
The basic steps
Top off the reservoir, then bleed one wheel at a time - usually starting furthest from the master cylinder - pushing old fluid out until fresh, clean fluid runs clear; see the bleeding order chart and bleeding basics. Keep the reservoir topped up the ENTIRE time - letting it run dry pulls air in and starts you over.
Safety and finishing
Brake fluid strips paint - wipe spills fast. Work on a securely supported car, never rely on a jack alone. When done, the pedal should be firm and high; if it is soft, you have air to bleed out - see spongy pedal after bleeding. Dispose of old fluid properly. Pair fresh fluid with quality pads and hardware.