dot 3 vs dot 4

Dot 3 vs Dot 4 – What is the difference?

In Brakes by Magnus Sellén1 Comment

dot 3 vs dot 4Your car features a hydraulic braking system to help you stop your car.

The brake pedal that you step on to start braking is attached to a piston in the brake caliper. It generates a large force that creates pressure in the brake lines.

The action of the brake line causes the attached rotors to compress the brake pads, creating enough friction to stop your wheels and bring your car to a halt.

Brake fluid plays a key role in managing the increased heat generated by the process that converts the kinetic energy of your vehicle into thermal energy.

There are two general types of brake fluids that can be produced on a silicone or glycol basis. Dot3 and Dot4 are popular glycol-based brake fluid options available for many vehicles. While Dot3 is popular with normal drivers, Dot4 is more common for racing cars and aggressive driving.

Dot3 vs Dot4: Which one is the better brake fluid?

Brake fluid is essential to keep your system working for a long time. It keeps components lubricated, ensuring a prompt response every time you step on the brake pedal.

A large amount of fluid compresses the rotors without difficulty when braking your vehicle, reducing the response speed and stopping distance. Both Dot3 and Dot4 brake fluids are commonly used for everyday cars. This Dot3 vs Dot4 overview section will help you find the best fluid for your braking system.

Dot3 is the more popular of the two types of brake fluids, but Dot4 is quickly gaining popularity because it is compatible with the standard traction control and anti-lock braking system. Although this aggressive braking action is not normally required for the average driver, it could help improve the traction control of your vehicle immensely.

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What is the difference between Dot3, Dot4 and Dot5 brake fluids?

Dot4 and Dot3 brake fluids are glycol-based products used in your braking system. They are hygroscopic and absorb water from the atmosphere, which means that care must be taken when storing and regularly replacing potentially contaminated fluids.

They are very volatile solvents for paints and eat away at the paintwork of your car. They can also be very reactive with other compounds in your car and should be stored safely.

Dot5 is silicone-based brake fluid. It does not absorb water from the air and is completely hydrophobic. It maintains its integrity and works well. It also has a higher boiling point than the brake fluids Dot3 and Dot4, making it more compatible with excessively aggressive driving.

However, it is not compatible with Dot3 or Dot4 liquids and should never be mixed. You must also follow the recommendations of your manufacturer to know whether your braking system is compatible with Dot5 brake fluid.

1. The Boiling Point

Dot3 has a lower boiling point, which means it is more likely to assimilate water. This leads to even lower boiling temperatures, which could lead to inefficient braking and damage the brake components over time. Dot4 has a higher boiling point and a lower water absorption capacity, which makes it better for your engine in the long run.

2. The Chemical Structure

chemical structure

The chemical structure of the brake fluids Dot3 and Dot4 will also vary. Dot4 is more tailored to water resistance, which makes it ideal for generally wet conditions. It also behaves relatively well in hot temperatures. The combination of glycol and borate will not corrode your brake components.

Dot3 consists of a mixture of polyalkene glycol and ether. It holds well in hot and dry or wet weather conditions. It is more suitable for regular driving than Dot4 brake fluid.

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3. The Boiling Capacity

The boiling capacity of your brake fluid is its ability to function well in a medium. Dot3 is not so sensitive to water and outdoors. However, Dot4, which has a low boiling capacity with water, will not provide ideal performance.

How to find the best brake fluid for your car

Always refer to your car repair manual to find out which brake fluid is best suited for your car.

You can choose between Dot3, Dot4, Dot5, and Dot5.1 brake fluid. So how do you know which brake fluid is the most suitable for your engine?

The boiling point of the brake fluid refers to the point at which it evaporates, which can make a difference when driving aggressively or in hot weather conditions. The boiling point of the brake fluid increases from Dot3 upwards, making it less suitable for heavy braking, such as in racing. However, Dot3 still offers enough power for regular driving.

Knowing your brake fluid options could help you avoid brake fade. Fluids with a lower boiling point tend to turn to gas more quickly and affect the operation of the braking system. Your ideal fluid should have a sufficient boiling point to cope with possible heat spikes.

However, this only applies to new oil from cans. Your ideal brake fluid should also have a high wet boiling point. This is determined by contaminating the fluid with approximately 3.7% water, which mimics the real contamination situations that many brake fluids are likely to be exposed to. Good brake fluid should have a high wet boiling point to ensure performance even under extreme conditions.

Conclusion

If you are a standard driver with a relatively straightforward driving schedule, Dot3 brake fluid may be more suitable for you. Dot4 would be ideal for drivers who deal with aggressive driving. Remember to keep your brake fluid away from the bodywork as it eats away at the paint and corrodes all parts it comes in contact with.

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Brake fluid also reacts poorly with other compounds and must be kept away from other vehicle fluids. It should also be kept in a tightly-closed container, as it could react with the water in the air. For this reason, you should not use brake fluid from an open container. You should also keep your brake fluid containers away from children.

Hello I'm Magnus, the owner and the writer of this website. I have been working with cars since I was 16 and I'm specialized with in-depth Automotive diagnostics. Also been driving drifting for the last 6 years. I'm here to give you answers to all your automotive questions and I hope that you enjoy our content.

1 thought on “ Dot 3 vs Dot 4 – What is the difference? ”

Comments
  1. I have a 1968 Kawasaki GT550 motor cycle which has been off the road for a number of years and the brake fluid from the front brake has drained from the reservoir and I aim to replace it. I have purchased a DOT 4 Synthetic Brake & Clutch Fluid is this suitable.

    Regards,
    Norman Snow.

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