DOT 3 and DOT 4 Fluid: What’s the Difference?

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Fluids like DOT 3 and DOT 4 require replacement at annual or biannual intervals, or else they would result in rusting inside the brake and damage other parts. The main purpose of these fluids is to transmit the pressure from the brake lever to the brake pads. Therefore, these fluids must be non-compressible. The fluids would allow the transfer of force effectively.

The brake fluid must lubricate the calipers to resist corrosion and maintain a high boiling point. A car owner can choose brake fluid from amongst its four types. Modern cars use hydraulic braking systems that use a special silicone-based braking fluid. 

Car accessories prefer this fluid, which is ideal when it interacts with other parts of your vehicle. The objective of the liquid is to provide outstanding performance under the harshest conditions.  

The Meaning of DOT

DOT or “Department of Transportation” refers to a classification chart of brake fluids as per their characteristics, performance, and safety levels. The system considers several factors, including the boiling point of the liquid and fluid composition. Experts use this system classification to ascertain the different types of fluids. DOT 3 and DOT 4 suit vehicles for daily use; therefore, they are the perfect choice for passenger vehicles. The brake fluid is an indispensable part of the car’s braking system. Therefore, choosing the suitable fluid for your vehicle is very important.

The Parameters of Difference

The jarring difference between the two fluids lies in their dry and wet boiling points. However, it is not just the difference in boiling point that functions as a factor to classify the two fluids. More intricate factors influence the fundamental difference between the two fluids. Would the difference affect the performance of the brakes of the vehicles? Can one mix the two fluids? Is the maintenance in both cases the same?

Different Boiling Points of DOT3 and DOT4 and What Do They Mean?

The dry boiling point of DOT3 is 401 degrees Fahrenheit. On the other hand, it is 284 degrees Fahrenheit for the wet boiling point. These approximate points mean the exact boiling points will vary. The fluid tends to exceed these marked points. This is the result of typically 80% glycol ether base, which contributes to water absorption.

For DOT4 fluids, the dry boiling point, as well as wet boiling point, remains significantly higher. Brake systems that heat up because of really fast speed can use this fluid to effectively tackle the overheating of the engine.

Such vehicles would include trucks or cars towing a heavy load. The absorption of moisture is more rapid than DOT3, therefore requiring frequent changing. DOT4 comes with a more concentrated glycol ether base at 50-65%, which aids in resisting the fluid’s boiling. To summarise, DOT 3 boils around 290°F while DOT4 would boil at 330°F- different boiling points even in the same moisture amount.

The Main Function of the Fluids

The silicone-based brake fluids generally have no colour or odor. The primary purpose of the brake fluid is to carry the force from your brake pedal to the brakes. If the brake fluid decreases in quantity or gets contaminated by other particles, it will not create enough pressure for the system to slow down or stop the vehicle. This could result in your vehicle becoming accident-prone. Therefore, it is advisable to change you’re the fluid in your vehicle now and then under proper expert inspection.

DOT3: A Deeper Analysis of Its Purpose

There is minimal rubber component swell in DOT3, reducing fluid loss and leakage. It is also corrosion protected, thus improving the brake system’s reliability and lifespan. This fluid is ideal for top-ups and refills of the clutch and the brakes in heavy commercial motorcycles, vehicles and 4WDs, and even passenger cars. Equipment for agriculture, mining, and construction can also use them.

Individuals can use the fluid when specified by the vehicle manufacturer. The fluid, naturally hygroscopic, absorbs water from the air, thus lowering the effectiveness of the product. Change the brake fluid as per the service guidelines of the manufacturer. Do not mix DOT3 brake fluid with Mineral or Silicone DOT 5. Since DOT3 has been around for the longest, it preferably has more popularity in the market.

DOT4: A Deeper Analysis of Its Purpose

The DOT4 is taking over since it is compatible with standard traction control and an anti-lock braking system. The glycol ether-based fluids of DOT4 have different borate esters. This assures better performance. Borate esters can improve the wet and dry boiling points. DOT4 has a more stable and higher boiling point compared to DOT3.

Changing the DOT4 every two years is advisable to maintain the brakes’ maximum safety. Water reduces the lifetime of a brake system. The moisture gets absorbed by the fluid through the brake hoses. When you keep using the brake system, it will heat the brakes. The boiling point decrease as the fluids continues to absorb water.

Do Not Fail to Change the Fluids Regularly

If the brake fluids are not changed regularly, it will cause the wheel and master cylinders to rust. One can mix the DOT 3 and DOT 4 without compromising performance and avoiding brake damage. They are glycol-based, so they will not cause any complications.

Even though they are compatible, it is still advisable not to mix them. The expert must remember that DOT4 is an alternate to DOT3. However, DOT3 is not an alternative to DOT4 and cannot become its substitute. Make sure to clean the reservoir before filling it with another type of fresh fluid.

Be sure to consult with the quality service of Carorbis to ensure that you are using the correct DOT 3 and DOT 4 fluid for your vehicle.

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