The most common brake fluid flush interval that I have seen over the years is 30k miles but every make and model may be different. Refer to your owner’s manual.
Yes. The most common reason you need a brake fluid flush is brake fluid absorbs moisture over time. Excess moisture in the old brake fluid will reduce your vehicle’s stopping power and cause corrosion.
They make test strips to determine if you need a brake fluid flush. You simply dip the test strip into your brake fluid and it will likely change color. The strips that we use to test brake fluid conditions will turn purple if moisture is present. There is a simple guide on the side of the brake fluid test strip bottle to use as a guide to determine if the moisture is high enough to warrant replacing your brake fluid.
This example is pulled from a 2017 Subaru Outback. Notice how the color on the strip is barely pink. This fluid is good.
Most car manufacturers suggest a brake fluid flush at certain mileage intervals. This interval can be found in the scheduled maintenance portion of your vehicle’s owner’s manual. Your trusted auto shop can also research the mileage interval as well.
One of the leading fluid suppliers has performed extensive studies and has found that if you perform your vehicle’s first brake fluid flush at 50k miles and then every 30k miles after that, you are far less likely to have major failures in your vehicle’s brake system. They feel so strongly about performing brake fluid flush as a regularly scheduled maintenance item that they offer participating shops a limited lifetime warranty on major brake components if the service is performed regularly utilizing their fluid and process. https://www.valvoline.com/recommended-auto-services/brake-fluid-service
Safety- The brake system on your vehicle is arguably the most important system to keep you safe while driving your vehicle. Performing a brake flush when needed is an inexpensive and easy way to keep your brake system performing properly. Old brake fluid absorbs moisture over time. Moisture in your brake fluid lowers your braking power and increases your stopping distance.
Another reason why it is a good idea to flush your brake fluid regularly is preventative maintenance- Moisture in your brake fluid also causes corrosion. Corrosion in your brake system will lead to premature failure of important and often expensive brake components like brake calipers, brake master cylinder, wheel cylinders, and abs components. I feel strongly that it is always best to perform regularly scheduled maintenance to not only keep your vehicle safe but to avoid as many problems as possible. This includes keeping good clean brake fluid in your vehicle before it builds up excessive moisture in the old brake fluid. Over the years of owning numerous vehicles, I have found my cost of ownership to be much lower if I perform regularly scheduled maintenance to avoid failures rather than waiting until my vehicle has a major failure.