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Brake Fluid – Types and purpose explained

Brake Fluid.being poured brake fluid reservoir

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What does Brake fluid do?

Brake fluid is a vital component of any vehicle’s braking system. It is a hydraulic fluid that transfers force from the brake pedal to the calipers or drums to stop the vehicle. It has a high boiling point and low compressibility, which allows it to withstand the high temperatures generated by the pads or drums. Without brake fluid, the pedal would be ineffective in stopping the vehicle. It also helps lubricate and protect th system’s internal components from corrosion and wear.

What are the different types of brake fluid?

There are several types of brake fluid available on the market, with the most common being;


DOT3 – a glycol-based fluid suitable for most older passenger vehicles, where a lower boiling point is okay.


DOT4 – a glycol-based fluid with a higher boiling point and is required for most modern vehicles or those that tow heavy loads.


DOT5 – a silicone-based fluid typically used in military vehicles and high-performance racing vehicles.

The type of brake fluid used in your vehicle depends on the make and model, the driver’s specific needs, and the driving conditions. It is important to always use the brake fluid recommended by the manufacturer and to adhere to the recommended service intervals for changing the fluid to ensure optimal performance and safety.

How often should I change my brake fluid?

The answer varies depending on the vehicle and the type of brake fluid used. It is generally recommended that car brake fluid be changed every two to three years or every 30,000 miles, whichever comes first. Over time, brake fluid can absorb moisture which will result in decreasing braking performance and can potentially cause damage to brake components. Changing the brake fluid is a relatively simple process that can be done with just a few tools.

10 Quick Steps to change your brake fluid

Please note: APD cannot accept any liability for advice or steps given. If you are not confident carrying out these steps, please consult a mechanic or local garage.

  1. Gather the necessary tools and supplies, including a turkey baster or syringe, a wrench, a container for the old brake fluid, and a fresh bottle of brake fluid recommended by the manufacturer.
  2. Locate the brake fluid reservoir under the hood of the car and remove the cap.
  3. Use the turkey baster or syringe to remove as much of the old brake fluid as possible from the reservoir.
  4. Refill the reservoir with fresh brake fluid up to the “Max” or “Full” line.
  5. Locate the bleeder valves on each brake caliper or wheel cylinder.
  6. Place a small hose over the bleeder valve and submerge the other end in a container of brake fluid.
  7. Use the wrench to loosen the bleeder valve and have a helper press down on the brake pedal. As the pedal is pressed down, brake fluid will be forced out through the bleeder valve and into the container.
  8. Tighten the bleeder valve and repeat the process on all four wheels until clean fluid is flowing out of the bleeder valve.
  9. Top up the brake fluid reservoir as needed and replace the cap.
  10. Test the brakes and make sure they are working properly before driving the car.

What happens if I don’t change my brake fluid?

Over time, brake fluid can absorb moisture, which can cause the boiling point to decrease and the fluid to become less effective. This can lead to a spongy brake pedal and reduced stopping power. Additionally, the moisture can cause corrosion inside the braking system.

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