Home Diagnosis and TroubleshootingBraking System DOT 3 Vs DOT 4 – Which Brake Fluid Is Right For You?

DOT 3 Vs DOT 4 – Which Brake Fluid Is Right For You?

by Jordan Harris
DOT 3 Vs DOT 4

Do you recognize the difference between DOT 3 vs DOT 4? Most of us drive 15,000 to 20,000 miles each year, and during that time, we’ve definitely changed our engine oil, checked our coolant levels, replaced our wiper blades (with some pointers on how to change windshield wipers), and possibly even had our brake pads and rotors examined?

Brake fluid is a sort of hydraulic fluid that activates the braking system of a vehicle. It is a non-compressible fluid that is kept in the brake lines and exerts pressure on each of the vehicle’s rotors.

It lubricates the braking components, allowing them to respond quickly when you press the brake pedal. The piston can gently compress the rotors with the aid of the fluid to slow down the vehicle.

The most popular brake fluid types in autos are DOT 3 and DOT 4. If you’re trying to select between DOT 3 vs DOT 4 brake fluid a comparison of the two will help you make a better decision.

What Exactly Is Brake Fluid?

When we press on the brake pedal, our car’s brake system is controlled by the brake fluid, which is a hydraulic fluid. As a force-transmitting fluid, the brake fluid must be non-compressible at all times in order to efficiently convey braking force to the wheels. Brake fluids must have very high boiling points since they are subjected to extremely high temperatures during braking.

Brake fluid is a glycol-based lubricant that stays liquid even when it freezes and performs well as a hydraulic fluid at high temperatures. It is expected to function in both the frigid winter and the scorching summer months. It’s a flexible fluid that can be used in a variety of temperatures.

Brake fluid, on the other hand, takes moisture from the air via microscopic pores in brake lines and a small vent in the reservoir. In fact, the moment brake fluid is injected into your braking system, it starts to absorb moisture.

What Is Brake Fluid Made Of

Brake fluid is made up of three primary components:

  • Solvent Ratio 60-90 Percent
    • Polyglycols have a high viscosity, which necessitates diluting them with a low viscosity substance (polyglycol ethers). Polyglycol ethers ensure that the fluid has a solvent. They must dissolve polyglycols and all other materials in a single-phase fluid capable of providing adequate lubrication at all temperatures.
  • Lubricant Ratio 5% to 30%
    • In brake fluids, polyglycols are utilized as lubricants in proportions of up to 30%. Alkylene oxides (ethylene and propylene) are combined with bifunctional components such as diols or water to produce them.
  • Additives 2% to 5% Of Total
    • Additives can be found in brake fluids up to 5% of the time. Corrosion inhibitors are used to preserve the metals in the brake system from corrosion, and antioxidants are used to slow the oxidative breakdown of glycol ethers and polyglycols and to delay the development of acidic decomposition products and resins. These two types of inhibitors are required to provide long-term and excellent brake fluid service life.

What Does The Dot In Brake Fluid Indicate?

The DOT rating system, which is used to categorize different brake fluid types of braking fluids based on their performance qualities and safety attributes, is represented by the ‘DOT’ in brake fluid.

To decide which class a fluid belongs in, this rating system considers a number of parameters, including the boiling point and composition of the fluid. Because of their performance under specific conditions, some braking fluids may earn a higher DOT grade than others.

DOT 3 Vs DOT 4

Some silicone-based DOT 5 brake fluids, for example, are known for having extremely high boiling temperatures, making them ideal for use in vehicles that will be driven in extreme heat or other harsh conditions.

Lower-grade DOT 3 and 4 lubricants, on the other hand, are typically recommended for daily usage in most passenger vehicles. Brake fluid is an important part of your vehicle’s braking system, and selecting the right type for your needs is key. Make sure you’re using the correct DOT-rated fluid for your car by consulting a trained mechanic.

Function Of Brake Fluid

It’s important to understand what brake fluid is and what it accomplishes before we get into the differences between DOT 4 brake fluid vs DOT 3. This will demonstrate how different ratings affect your brake system’s performance.

The majority of autos employ hydraulic braking. Braking fluid is transferred to your calipers, which press the pads against the rotors when you press down on the brake pedal. As you apply greater pressure to the brakes, the pads and rotors produce more friction, causing the automobile to come to a speedier stop.

Without brake fluid, you’ll be unable to stop. Brake fluid should also be changed on a regular basis because it deteriorates over time. It can absorb moisture, causing brake failure. Brake system failure, which can be fatal, can be caused by contaminated braking fluid. Finally, it’s vital to keep your brake fluid up to date in order to drive safely.

It’s easy to see why moisture is such a problem for the fluid. Fresh brake fluid has a higher boiling point than the temperature produced while braking. Water, on the other hand, has a far lower boiling point and can boil as a result of the high temperatures produced by braking.

When moisture is absorbed by the brake fluid, it has the ability to boil and produce gas. When you apply pressure to your brake pedal, the gas in your braking system contracts rather than forcing brake fluid into your rotors.

Boiling brake fluid may lead you to hit the brakes and the pedal to drop to the floor, causing the vehicle to speed up. This is why changing your brake fluid on a regular basis is so important.

Brake Fluids: DOT3, DOT4, And DOT5

For most cars, there are three brake fluid types on the market. The DOT3 is the most basic, and the DOT5 is the most sophisticated, with richer ingredients. Therefore the range grows in terms of performance in ascending order. In our ordinary vehicles, however, DOT4 is now the standard.

DOT 3 Vs DOT 4

1. Explaining DOT 3 Brake Fluid

The most common type of brake fluid on the market is DOT 3. Glycol makes up around 80% of DOT 3 brake fluid, with other chemicals accounting for the remains. The DOT 3 brake fluid is frequently yellow in hue.

There are no hard and fast rules for DOT 3 or any other braking fluid, and boiling points differ from brand to brand. In a nutshell, the dry boiling point of DOT 3 fluid is 205 degrees Celsius, and the wet boiling point is 140 degrees Celsius.

When fluid has accumulated moisture over time, the wet boiling point is taken into account. DOT 3 fluid, on the other hand, acquires less moisture over time than DOT 4 fluid.

2. Brake Fluid DOT 4

DOT 4 brake fluid is often a glycol ether-based fluid with borate esters added. The combination of these substances is intended to improve the function of your vehicle’s brakes. Because the borate esters boost the dry and wet boiling points of your brake fluid, DOT 4 brake fluid comes with the ability to handle greater temperatures out of the box.

A dry boiling point temperature of 230°C (450°F) and a wet boiling point temperature of 155°C (just over 300°F) is normal for DOT 4 brake fluid. Car racers frequently use DOT 4 brake fluid in their vehicles.

DOT 4 brake fluid, on the other hand, should only be used if your car’s manual specifies it or if you’re driving a European vehicle. Do you have trouble distinguishing between DOT 3 vs DOT 4 water absorption? DOT 4 brake fluid absorbs more water than DOT 3 brake fluid and has a blue color rather than an amber hue like DOT 3 brake fluid. This is also a useful way to distinguish between the two.

3. Brake Fluid DOT 5

DOT5 Brake Fluid is used in high-performance vehicles designed to handle high-intensity situations. DOT5 is a wholly synthetic silicone-based braking fluid that contains no moisture. Both DOT3 and DOT4 brake fluids have less compressibility.

DOT5 brake fluid also has a higher boiling point, with a dry boiling temperature of 260 degrees Celsius and a wet boiling point of 180 degrees Celsius. It is the most long-lasting brake fluid since it does not contain moisture and delivers great braking performance with a longer replacement period.

However, some manufacturers are also producing wholly synthetic DOT4 brake fluids, which have higher boiling temperatures than DOT5 and are therefore better for on-road use.

What’s The Difference Between DOT 3 Vs DOT 4

The Department of Transportation (DOT) number for these glycol-based braking fluids is 3, 4, 5.1. Because there are no specific legal criteria, these braking fluids do not need to be classified by chemical makeup. As a result, there is no standard brake fluid composition. Having said that, they must meet specific federal standards.


The parameters cover equilibrium reflux boiling point (dry and wet boiling points), kinematic viscosities, pH values, high-temperature stability, chemical stability, corrosion, water tolerance, compatibility (sludging, sedimentation, and crystallization), and oxidation resistance.

DOT3 is the most common type of brake fluid used by regular drivers. This type may be found in the majority of automobiles and trucks. It’s basically for vehicles that don’t use their braking system aggressively, in other words, they don’t convert kinetic energy into heat that DOT 3 can’t handle.

DOT4 is used in racing and police enforcement vehicles because it has a higher boiling point. Because of the rising use of ABS and traction control, DOT4 has begun to gain in popularity.

1. Boiling Points

The boiling point is the main distinction between DOT3 and DOT4. This is the temperature at which the fluid evaporates, as well as its susceptibility to water absorption. DOT3 and DOT4 are both hygroscopic, which means they absorb moisture.

DOT3 is more susceptible to water absorption because of its lower boiling point. As a result, DOT3 boils significantly more easily under hard braking. Boiling points are classified as dry or wet. Using fluid from a brand-new container, the dry boiling point is determined.

The wet boiling point, on the other hand, is determined using a 3.7 percent water-contaminated solution. The latter is a realistic scenario as specified by the Department of Transportation in their testing environments.

Keep in mind that moisture may enter the system every time you remove the reservoir top to add fluid. As a result, the quality of your fluid will degrade. So be sure to clean the braking system every now and then to get rid of the moisture.

Wet boiling points of brake fluids: DOT3 140°C (284°F); DOT4 155°C (311°F); Super DOT 4 195°C (383°F); DOT 5.1 185°C (365F).

2. Chemical Compositions

As previously stated, there are no exact chemical structural requirements as long as they match the standards we provided. Diethylene glycol is commonly used in DOT3 brake fluid. This isn’t a requirement, but it appears to be the most cost-effective approach for manufacturers to achieve the standards.

In other words, the braking fluid business has self-regulated and established this as the industry standard. Glycol and borate ester make up DOT4. The borate in the braking fluid permits it to withstand higher temperatures.

3. Strengths

DOT 3 brake fluid has a high dry boiling capacity as well as a high wet boiling capacity. When the fluid is exposed to the air and water, it reacts swiftly and effectively. DOT 4 brake fluid performs better with a dry boiling capacity but not as quickly with a wet boiling capacity.

It’s critical to comprehend the function of these seemingly tiny components, which are critical to the operation of your vehicle’s system. Your car’s brakes are possibly the most vital component to maintain in excellent operating order, and understanding how they operate is crucial.

While both DOT 3 and DOT 4 are glycol-based fluids, DOT 3 is thought to have a longer life under the correct conditions than DOT 4. Glycol-based fluids aren’t generic; they’re a blend of several different compounds, with up to ten different constituents combined in.

The viscosity of DOT 4 fluid is higher than that of DOT 3, and it can sustain fluidity at higher temperatures. The viscosity of a fluid is a measurement of its resistance to flow. Because of its high viscosity, DOT 4 fluid has a great temperature resistance and durability.

4. Performance

DOT 3 fluid has a higher tendency for absorbing water than DOT 4 fluid. As a result, it’s more prone to boil while braking hard, affecting braking performance. This is why DOT 3 fluids are not advised for use in vehicles that are subjected to a lot of abuse, such as racing automobiles, heavy-duty trucks, and commercial trucks.

DOT 3 is considered to have a longer lifespan than DOT 4 under ideal conditions. The addition of borate to the DOT 4 fluid, on the other hand, aids in the proper functioning of the complete braking system, boosting the vehicle’s overall performance.

5. Boiling Capacity

In this DOT 3 vs DOT 4 brake fluid comparison, DOT 3 comes out on top. Because it has both wet and dry boiling capacity, it works effectively in both water and open air. Although DOT 4 has a high dry boiling capacity, it does not perform well in water.

Which one do you think you should pick? Is DOT 3 or DOT 4 brake fluid preferable to use? If you’re driving a regular vehicle, the first option is the best. However, DOT 4 will take very good care of the braking parts if it’s a racing car or you enjoy harsh driving.

Is It Possible To Utilize DOT 5.1 Brake Fluid?

DOT 5.1 brake fluid has a wide range of applications and can be used safely in any brake system that calls for glycol ether fluid. This includes the latest generation of fully electric and hybrid vehicles, as well as high-performance European vehicles with low conductivity. It is totally compatible with DOT 4 and DOT 3 fluids and can be used to replace or supplement them.

Because DOT 4 and 5.1 are both glycol-based brake fluids, they can be used together without causing serious damage to your brake system. DOT 5.1 brake fluid (glycol-based) must never be mistaken with DOT 5 brake fluid (silicone-based), which should not be coupled with any other DOT fluid. DOT 5 brake fluid is mostly used in historic cars that are kept in storage for lengthy periods of time and require a water-resistant braking fluid.

What Is The Impact Of Moisture On Braking Performance?

Incompressible fluids are another name for brake fluids. It’s the primary property in charge of transferring force from the brake pedal to the brake calipers. If the fluid is compressible, the pressure will not reach the brake calipers as quickly as it should, resulting in decreased braking performance.

We are all aware that moisture is compressible and may develop into gas under pressure, which is where the troubles begin. When moisture is added with brake fluid, it affects its incompressible quality, and when pressure is applied, the moisture expands and compresses, reducing braking force.

With a lot of free motion on the braking pedal, having a lot of moisture can even make the braking system redundant. As a consequence, it is always recommended that the brake fluid be changed on a regular basis and that the fluid storage lid be kept tightly closed.

Brake Fluid Facts: What You Need to Know

  • The U.S. Department of Transportation classifies brake fluid into four categories: DOT 3, DOT 4, DOT 5, and DOT 5.1.
  • The primary difference between DOT 3 and DOT 4 brake fluid is their respective boiling points.
  • DOT 3 brake fluid is the most common type used in cars and trucks, while DOT 4 is gaining popularity due to its lower viscosity.
  • DOT 3 and DOT 4 brake fluids are compatible, but DOT 4 offers a higher boiling point than DOT 3.
  • DOT 5 brake fluid is silicone and doesn’t absorb water, making it incompatible with the other brake fluids and used mostly in classic cars.
  • High temperatures can vaporize brake fluid and cause brake fade, leading to a spongy feeling when applying the brakes.
  • The boiling point of brake fluid indicates the temperature at which the fluid vaporizes, with higher DOT classifications having higher boiling points and better resistance to heat.
  • Brake fluid is hygroscopic, meaning it absorbs water, and its wet boiling point is lower than its dry boiling point due to contamination from water.
  • Moisture can enter the brake system through worn seals, rubber brake lines, and when adding fluid, causing corrosion in metal components and making brakes unsafe.
  • It’s recommended to change brake fluid every two years in passenger vehicles and at least every year in racing vehicles to prevent spongy brakes, corrosion, and brake failure.


Here are some popular FAQs:

Can You Mix Dot 3 And Dot 4

The short answer is that you can combine DOT 3 and DOT 4 brake fluids. Both DOT 3 and DOT 4 are glycol-based brake fluids that can be combined together. However, it’s usually best to follow the manufacturer’s instructions.

DOT 3 Vs DOT 4 Which Is Better

In DOT 3 vs. DOT 4 brake fluid comparison, DOT 3 comes out on top. Because it has both wet and dry boiling capacity, it works effectively in both water and open air. Although DOT 4 has a high dry boiling capacity, it does not perform well in water.

Difference Between DOT 4 Brake Fluid Vs DOT 3

DOT 3 vs DOT4 brake fluid can be differentiated through DOT 3 brake fluid’s absorption of less water from the air than DOT 4. Hence, it necessitates fewer fluid changes. Also, there are the higher dry and wet boiling temperatures of DOT 4 brake fluid make it appropriate for usage in hotter settings. Finally, the difference between DOT 3 and DOT 4 brake fluids is their capacity to withstand heat and water absorption. Check your owner’s manual to see what sort of brake fluid your car requires when it’s time to change it.

Does Brake Fluid Go Bad

Brake fluid does have the potential to become contaminated. Brake fluid absorbs moisture, reducing its effectiveness. As a result, changing brake fluid every two years is recommended. Brake fluid, on the other hand, is one of the most largely overlooked maintenance items. Brake fluid is rarely changed before it becomes contaminated. They frequently wait until the wear indicator on the brakes makes a grinding sound before changing the brake pads and bleeding the brakes.

What Brake Fluid Do I Need

The most widely used is DOT 3. It has existed for quite some time. DOT 3 brake fluid is thought to have the standard measurements needed to maintain a car’s typical braking system. Because of their chemical components, they can withstand heat up to a particular degree. DOT 4 brake fluid functions similarly to DOT 3 brake fluid, but it is a superior fluid since it can handle difficulties caused by the production or poor use of other brake fluids, making it a more reliable component.

Final Verdict – DOT 3 Vs DOT 4

DOT 3 Vs DOT 4

While both DOT 3 vs DOT 4 are glycol-based fluids, DOT 3 is expected to have a longer lifespan than DOT 4 when used properly. The DOT 3 fluid, on the other hand, has a higher inclination for water absorption than the DOT 4 fluid. As a result, it’s more prone to boil while braking hard, affecting braking performance.

This is why DOT 3 fluids are not suggested for use in vehicles that are driven hard. Because of its high viscosity, DOT 4 exhibits exceptional tolerance and stability at high temperatures, assisting in the correct operation of the whole brake system.

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