What Are The Differences Between DOT 3 vs. DOT 4 Brake Fluid?

Brandon Trenton

Updated on:

Differences between DOT 3 vs. DOT 4 Brake Fluid


Since this whole piece of writing is based on the differences but it does not seem to have much distinction. Both of them are brake fluid. It is a significant part of learning the difference to know about the operations and functions of the brake fluid. The brake fluid is basically a hydraulic fluid and hydraulic clutch used in all automobiles.

What are DOT 3 and DOT 4?

Dot 3 and Dot 4 are the types of brake fluid that are hygroscopic in nature being used for the automotive disc, drum, and anti-skid brake system.

What is the Function of a Brake Fluid?

The function of brake fluid:

  1. It is generally structured to guard the metals utilized inside parts such as calipers, wheel cylinders, and so forth.
  2. It helps to maintain a low level of compressibility even with changing temperature.
  3. They absorb moisture from the atmosphere.
  4. Its hydraulic fluid controls the mechanism of braking.

Let’s take a simple example; when you push the brake pedal in the car, this force results from another force in the brake line. Later, it leads the rotor to squash the pads. Now, this resistance leads the wheel into the stoppage of turning. Ultimately, the car or other vehicle stops. Lastly, it turns the kinetic energy into heat energy where the brake fluid plays its part.


The Differences between DOT 3 and DOT 4

1. The Changing Boiling Point:

The main or distinctive feature between the two is their boiling point. It is basically the heat that that fluid vaporizes. Consequently, it leads to a change in the water absorption feature. However, they both are hygroscopic in its character. The DOT 3 has the least boiling point and inclines to absorb water.

Two Kind of Boiling Points:

In addition to it, there are two kinds of boiling points i.e. dry and wet. The dry means that the fluids belong to the new vessel. While the other belongs to the 3.7% water which has been contaminated. These two are the boiling point which happens whilst usual driving.

Notably, whenever you open the reservoir lid to pour fluid, its quality will reduce. You are required to cleanse your brake system so that its original good condition does not decline.

2. Steaming Capability

Since we have already discussed that DOT 3 has two different boiling points i.e. dry and wet So, it needs to be dealt with accordingly. Both brake fluid has a distinct boiling capacity. Conferring the DOT 3, it can perform well in both of the boiling types. This is used in regular drives.

Whilst the DOT 4 is utilized in racing and has a high dry boiling point.  In case, you want to go on a rough drive then use Dot-4 since it takes care of all braking parts.

3. Chemical Compositions.

So, here comes a huge change in chemical composition. The DOT 3 and 4 are differentiated by its chemical structure. The dOT-3 is made up of Diethylene Glycol (DEG) while the DOT-4 is made of glycol and borate ester. This chemical composition brings a difference in its usage too.

The DOT-4’s borate ester assists the fluid to tackle with high-heat and cold. Further, both boiling points incline to be higher, and the chemical compositions aids to simplify the high-level of water resistance and constancy under high temperatures.

4. Precautionary Measures

There are certain precautionary measures to take care of when concerned about the brake fluids.

  1. Firstly, do not keep the fluid exposed since the quality is declined
  2. Secondly, Cover or sealed it completely while storing it somewhere
  3. When pouring the fluids, look after that it is not spilled up on the car as they also come through paints.
  4. Forth, you need to prevent it from mixing with other fluids since it might depict a bad reaction.
  5. Lastly, prevent taking brake fluids from an exposed container.


Frequently Asked Questions Regarding Brake Fluids

What are the categories of brake fluid?

The glycol-based brake fluid is further categorized into statistical types: 3, 4, 5, and 5.1.

What is the formula for brake fluid?

There is no such standard formula yet formulated for brake fluid. But they have to come over particular criteria set by the higher legal authorities.

What are the standard requirements to meet?

The limits and ranges set for pH values, chemical stability, water intolerance, and oxidation resistance need to be met.

What is the ideal brake fluid used by routine drivers?

The regular or routine drivers utilize DOT 3 brake fluid. It is recommended for that automobile that does not utilize their braking system harshly.

DOT 4 is utilized by police officers mostly meanwhile this brake fluid has a higher boiling point.



In the enclosure, the key distinction between the two brakes fluids is its material’s boiling points. It is recommended to change the brake fluid with time since its quality is degraded. However, you do not change the fluid; it can cause a negative effect on your brake system i.e. harmful. Moreover, the moisture leads to corrosion of the metal parts.

While other regular driving cars, they need to alter the fluid annually. However, this is mostly neglected by every next car owner.

When you are unaware of altering the brake fluid then you can use the booklet of instruction from the manufacturer’s end. Thus, there is no such difference except the boiling point, chemical compositions, and the boiling capacity which in really affect the functioning of brake fluid somehow.

Leave a Comment