DOT 3 vs. DOT 4 Brake Fluid: Differences and When to Use Them

In this DOT 3 vs. DOT 4 brake fluid article, you will discover the main differences between both brake fluids and when they can be used.


DOT 3 and DOT 4 brake fluid may not appear to differ much, but there are several differences that you should be aware of. You must first understand how brake fluid works in an automobile. Brake fluid is a hydraulic fluid that is essential to the braking system. It exerts pressure on the rotors in each corner of the car by being stored in the brake lines.


In your car, pressing the brake pedal with force creates pressure in the brake line. This squeezes the brake pads against the rotors. The wheels cease rotating as a result of this friction, and the car comes to a stop. The braking fluid then enters the picture as the kinetic energy is converted into thermal energy as a result.


How Brake Fluids Work

When we apply brakes, a piston in the brake caliper is compressed in a hydraulic brake system. The brake rotors press on the brake pads as a result of the pressure created by the brake pedal inside the brake lines. As a result of the friction, the wheels cease rotating and the vehicle comes to a stop. The braking fluid is used to convert the kinetic energy of the vehicle during this friction into heat energy.


There are many different kinds of brake fluids, but they can all be divided into two categories: silicone-based and glycol-based. By grade, these can also be divided even further.


Both DOT3 and DOT4 are glycol-based brake fluids. Only automobiles lacking anti-lock brake systems can use silicone-based brake fluids.


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Differences Between DOT 3 and DOT 4 Brake Fluid

Boiling Point

The boiling point is the main difference between DOT 3 and DOT 4 brake fluid. Both of them are hygroscopic, which means that this affects how much water they absorb. But DOT 3 prefers to absorb water since it has a lower boiling point.


Hard braking has more potential to boil. Dry and wet boiling points are the two different sorts. The former refers to a fluid that has just been placed in a container, whereas the latter refers to a fluid that has been tainted with 3.7% water. The boiling point that will happen while driving normally is the second of the two. The quality will decrease each time you remove the reservoir cover to add fluid. If you want to keep the brake system in good shape, you should flush it out sometimes.



Both its dry and wet boiling capacities are extremely high for DOT 3 brake fluid. When the fluid meets air and water, the reactions happen quickly and well.


When it comes to wet boiling capacity, DOT 4 brake fluid reacts more slowly than when it reacts with a dry boiling capacity.


It is important to understand the function of these parts. The brakes on your car are possibly the most crucial component that you must keep in good working order, so it’s crucial to know how they operate.


Chemical Formulation

Another DOT 3 vs. DOT 4 brake fluid difference is in their chemical compositions. The former frequently use diethylene glycol as a basis. Although it is not a requirement, manufacturers of brake fluid appear to have adopted it. When it comes to DOT 4, it typically contains glycol and borate ester. The fluid can withstand higher temperatures thanks to the latter ingredient. The chemical components contribute to a high level of water tolerance and stability under high temperatures, and both the dry and wet boiling points tend to be higher.


Car Models

Since economy automobiles often need less stopping power and drivers don’t frequently use hard braking, DOT 3 brake fluid is used in most of them.


However, since they all stop more abruptly and frequently, you might expect to see DOT 4 brake fluid in police cars, motorcycles, and racing cars. Always abide by the brake fluid type recommendations made by the vehicle’s manufacturer.


Boiling Capacity

Both the wet and dry boiling capacities of DOT 3 brake fluid are excellent. This means that the fluid will work well when it comes in contact with water and fresh air.


When it comes to dry boiling capability, DOT 4 brake fluid excels. Unfortunately, it doesn’t have a very high wet boiling capacity.


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Can DOT 5 Be Combined with DOT 3 and DOT 4?

A silicone-based braking fluid is called Dot5. It is incompatible with ABS systems and does not absorb water from the atmosphere. It functions effectively and keeps its integrity. Also, because it has a higher boiling point than Dot3 and Dot4 brake fluids, it is better for driving with a lot of speed.


It should never be combined with Dot3 or Dot4 liquids since they are incompatible. You must also follow the manufacturer’s instructions to find out if your brake system will work with Dot5 brake fluid.


DOT 3 vs. DOT 4 Brake Fluid: Which is Superior?

Of the two brake fluids, Dot3 is more widely used, but Dot4 is swiftly catching on thanks to its compatibility with the industry-standard traction control and anti-lock braking systems.


Dot 4 is better for all uses because it has a higher boiling point. Even though it is often a little more expensive, it is worth buying.


Wrapping Up

As a general rule, the difference in the boiling points is what distinguishes DOT 3 brake fluid from DOT 4 brake fluid. Keep in mind that brake fluid can deteriorate over time, so you should make a point of refilling it sometimes. If you don’t, the moisture may wind up corroding the metal parts of your automobile and causing your brakes to become spongy and hazardous.


A decent rule of thumb is to replace the fluid in typical passenger cars every two years. However, you should develop the habit of replacing the brake fluid once a year if you drive a professional-grade racing car. Take this blog post about DOT 3 vs. DOT 4 brake fluid as a reminder to take care of this important part of your car, since most car owners tend to ignore brake maintenance.

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