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Brake Fluid – Types and Functions explained

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What does Brake fluid do?

Brake fluid transfers hydraulic pressure from the brake master cylinder to your brakes, allowing you
to control your stopping speed when driving. It can also be used for clutch fluid in most manual
transmission vehicles. Please do check your vehicle manual or the cap of the clutch fluid reservoir
which should indicate if a special fluid is needed

What are the different types of brake fluid?

There are a number of different types of brake fluids which have different “dot” ratings. The
essential difference between the fluids is the Dot manufacturers are required to meet specific
criteria relating to a fluid’s minimum dry and wet boiling points depending on the dot number on the
bottle. These boiling points indicate the minimum temperature a brake fluid can perform at before
the brake fluid starts to boil – which can lead to brake failure. As a rule of thumb the higher the dot
the higher the boiling point. As engines have become more modern and complex the dot used has
gone up so where as an older engine would use a Dot 3 or Dot 4 fluid, these fluids will no longer be
able to cope with modern vehicles so a higher Dot rating is needed to ensure the braking system is
safe and performs as expected when needed.

How often should I change my brake fluid?

Manufacturers recommend changing your brake fluid every 1 to 2 Years as over time the fluid will absorb water which will slowly erode the performance of the fluid and decrease its boiling point. Water-contaminated brake fluid causes vapour bubbles to develop, which eventually applies force to the brake pedal, making your brakes feel spongy.

View APD’s full range of brake fluid…

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