This article is intended to give you both a sense of what you need to do to make sure your brake fluid is in good shape and will allow your car to stop safely, and also a bit about how brake fluid works. There are a few aspects of brake fluid where understanding more about it helps you know what to do, and not do, when you're authorizing repairs or working on the car yourself.
The Basics: What you need to do to stay safe
Here's the need-to-know stuff. First of all, your brakes don't work without brake fluid. It's a hydraulic system. Brake pressure pushes fluid down to your brakes, pushing the pads onto the rotor (these are called disc brakes, because the rotor looks like a disc). The rotors are attached to the wheel hubs, and spin as the wheel turns. More pressure causes the car to slow down. No fluid, no pressure. You have an emergency brake (also known as a parking brake), but it's often too weak to really stop the car in an emergency. So if you or your mechanic spot a brake fluid leak, it's a big deal. You should fix it immediately, and you should not drive it until it is fixed. An important way to also know about the status of your brake fluid is using the Brake Fluid Tester.
If there are no leaks, you may still have issues. Brake fluid, over time, goes bad. It absorbs water from the air, and this causes gunk like rust to build up. Water also has a much lower boiling point than brake fluid. If you are braking really hard, the water might boil in the lines carrying the brake fluid to the brake components. If that happens, you could "lose" your brakes – the pedal might flop onto the floor, and the car won't stop.
Car makers and brand has recently recommend the use of Car Brake Fluid Tester to be used in determining the quality car owners' brake fluid. This device helps to determine whether to completely bleed the brake fluid or still retain it as it shows the status. Click here to see how the device works.
The brake fluid change interval varies, but a good rule of thumb is every other year. Ask for a brake fluid change when you get an oil change after the right amount of time has passed. It's usually not expensive if you have a typical braking system.
Lastly, if you're topping off a low brake fluid reservoir, only use brake fluid from a fresh container. Brake fluid starts to "go bad" almost immediately, hence the need for a brake fluid tester. Luckily, regular fluids are inexpensive. Buy only what you'll use relatively soon. Brake fluid lasts for about 2 years in an unopened container.