Brake Fluid Types: The Difference Between Different Brake Fluids, Pros And Cons Explained

Brake Fluid is one of the most important components when it comes to your vehicle’s braking system. A lot of the time, it is also one of the components that we might forget to look at. There are different aspects to consider when it comes to our vehicles’ brake fluid. The type of brake fluid we need to use, when to replace it, when to top it up, and so forth. Here we discuss the different types of brake fluid in more detail.

What Is Brake Fluid?

“Brake fluid is a type of hydraulic fluid, meaning that it’s responsible for moving component parts within a system. When the brake pedal is pressed, the compressive effect builds pressure in the brake system, forcing the fluid to press down on the brake rotors, squeezing the brake pads to bring the car to a stop.

Because of the high-stress, high-friction nature of braking, brake fluid must operate perfectly at high pressures and temperatures. This makes it vital that brake fluid is regularly checked and maintained, ensuring good braking performance in any condition.”

What Affects Brake Fluid Performance?

“One of the biggest things which can inhibit the performance of a car’s brake fluid is moisture. As brake fluid ages it can absorb small amounts of moisture from its surroundings, including the air – this is called hygroscopic. If brake fluid becomes too full of moisture, problems can arise when the fluid becomes hot under braking, with the moisture turning to vapour inside the brake lines. This leads to a soft, spongy brake pedal feel, and will stop your car braking as well as it should.

You should change the brake fluid at least once every two years to keep your brakes working properly. You should also take care when you’re checking or changing the brake fluid, to ensure the fluid doesn’t come into contact with excessive air and moisture.”

Different Types of Brake Fluid

“The three main types of brake fluid now available are DOT3, DOT4 and DOT5. DOT3 and DOT4 are glycol-based fluids, and DOT5 is silicon-based. The main difference is that DOT3 and DOT4 absorb water, while DOT5 doesn’t.

One of the important characteristics of brake fluid is its boiling point. Hydraulic systems rely on an incompressible fluid to transmit force. Liquids are generally incompressible while gases are compressible. If the brake fluid boils (becomes a gas), it will lose most of its ability to transmit force. This may partially or completely disable the brakes. To make matters worse, the only time you are likely to boil your brake fluid is during a period of prolonged braking, such a drive down a mountain — certainly not the best time for brake failure!

As a DOT3 or DOT4 brake fluid absorbs water, its boiling point decreases. It can absorb water from the air, which is why you should avoid opening your car’s brake fluid reservoir. For the same reason, you should always keep containers of brake fluid tightly sealed.

DOT5 fluid does not absorb water. This means the boiling point will remain relatively stable, but it also means that any water that does get into your brake system will tend to form pure water pockets, which could cause brake corrosion.”

What do Brake Fluid DOT Ratings Mean?

“All forms of brake fluid are given a DOT rating. DOT simply stands for Department of Transport, which sets the safety regulations for the acceptable performance of different brake fluids. The DOT ratings given to brake fluids are based on the liquid’s dry and wet boiling points. As a rule of thumb, the higher the boiling point, the longer the lifespan of the brake fluid.”

Characteristics of DOT brake fluids:

DOT	Dry Boiling Point	Wet Boiling Point
DOT 2	190°C	140°C
DOT 3	205°C	140°C
DOT 4	230°C	155°C
DOT 5	260°C	180°C
DOT 5.1	270°C	180°C

“While it’s better to use brake fluid with a higher DOT rating, you should always refer to your car’s manual, as some brake fluids are incompatible with different brake lines and systems. Your manual will let you know which type of brake fluid to use.”

Related Tags: Brakes Repair

Additional Articles Of Interest Relating To Brake Fluid:

Brake Fluid Vs Clutch Fluid – Importance Of Both And Differences Explained

What Colour Should Brake Fluid Be?

Brake Fluid: How to Know When It’s Time To Have It Replaced

How to Check Your Car’s Brake Fluid Levels