5 Common Questions About Brake Fluid (Answered)

Whether you are a veteran racer or a first-time car owner, you probably know that your vehicle needs different types of fluids to function properly.

Brake fluid is one of the most important fluids that a car requires.

So, here are some of the most common questions that arise when you hear the word “Brake Fluid.”  

Is Brake Fluid Red?

As of today, companies do not offer brake fluid in red color. So, if you see a brake fluid with red color, it is probably old and dirty.

If you want to buy a high-quality brake fluid, you have to pay close attention to the color.

While replacing a brake pad or a master cylinder, you must invest your money into a premium type of brake fluid.

There are four types of brake fluids available out there: DOT 5.1, DOT 5, DOT 4, and DOT 3. All of these variations come with different properties and fluid colors, such as:

  • DOT 5.1 – This fluid is based on poly-glycol. It has a minimum wet boiling point of 1900C and a dry boiling point of 2700C. DOT 5.1 brake fluid usually comes with amber in color and is considered the best brake fluid out there.
  • DOT 5 – DOT 5 is a silicone-based brake fluid with a dry boiling point of 2600C and a wet boiling point of 1800C. It is a perfect pick for weekend collector vehicles, antique automobiles as well as military vehicles. 
  • DOT 4 – This one is also a poly-glycol brake fluid. It has a minimum wet boiling point of 1550C and a dry boiling point of 2300C. DOT 4 brake fluid is nearly clear with just a hint of yellow. It is a perfect pick for vehicles with high-speed braking systems, ABS systems, high altitude as well as towing.
  • DOT 3 – It is probably the oldest type of brake fluid available in the market. It has a minimum boiling point of 1400C when wet and 2050C when dry. When it’s new, this brake fluid usually comes in bluish color.

Is Brake Fluid Hygroscopic? 

There are no two brake fluids that are the same. Some types of brake fluids are hygroscopic, whereas others aren’t. At standard atmospheric pressures, glycol-based liquids are always hygroscopic, indicating they can absorb humidity or water from the surroundings.

The qualities and attributes of various vehicle fluids vary. When it comes to brake fluids, we always recommend choosing one that absorbs the least amount of moisture.

Hygroscopic fluids absorb moisture at a rate of 2 to 3% each year on average. In humid locations and circumstances, this process can be exasperating.

Moisture frequently comes into contact with brake fluid through microscopic pores found in seams, joints, seals, and brake hoses. When this water content is blended with brake fluid, the temperature and performance of the brake fluid are reduced.

The brake fluids DOT 4 and DOT 3 are hygroscopic. Moisture can impair the overall performance of these fluids occasionally.

Does Brake Fluid Evaporate?

Usually, brake fluids can withstand high temperatures, meaning they should not evaporate rapidly. That being said, like all other liquids out there, brake fluids can evaporate as well.

Brake fluids are made of a lot of ingredients, including esters and alcohol. Furthermore, these products can absorb moisture from the atmosphere, which increases the risk of evaporation.

Due to their various ingredients, we cannot make rock-solid rules about the evaporation process of brake fluid.

There are two main reasons why brake fluids can evaporate over time: their nature and ingredients. Most experts think this liquid evaporates.

Alternatively, some disagree as well. The correct answer to this question depends upon the quality of your selected fluid and your braking system.  

Does Brake Fluid Smell?

Brake fluid is probably the hardest to diagnose of all the vehicle fluids you regularly use in your car. Typically, brake fluids smell a little fishy. As most brake fluids are almost colorless, it’s rational to ask whether they stink or not. The best approach to find leaking brake fluid is through its scent.

It’s important to remember that brake fluid is primarily clear and colorless. Furthermore, if the leak is a minor one, you may not even notice it under your vehicle.

As a result, locating a leaking brake fluid is a difficult task. One of the most effective ways to find a leak is to smell it.

Brake fluids frequently have a fishy odor. This smell, on the other hand, isn’t really strong. You might not even notice it in most circumstances. This fluid may have a sweet-like aroma in addition to its fishy smell.

Apart from the scent, the consistency of braking fluid can also be used to determine leaks.

The viscosity of this liquid is usually similar to that of vegetable oil. So, if you see a vegetable oil-like substance under your automobile or a strange odor, don’t panic. It might be the right time to find a repair shop that will diagnose your problem more thoroughly.

Does Brake Fluid Circulate?

No, brake fluids do not circulate at all. This liquid generally flows in one direction: from the brake to the master reservoir to under it. Afterward, brake fluid flows out towards wheel corners. So, if you are wondering, do brake fluids circle back to the master cylinder? The simple answer is NO.

The most significant reason as to why brake fluid does not circulate is that this liquid absorbs moisture over time. As humidity can reduce the boiling points of brake fluid, it can make it vulnerable to heat damage. That can affect your whole vehicle. 

To protect your car from severe damage, you need to flush out the brake fluid from time to time.

It’s noteworthy to mention that you must flush out the old fluid before adding the new one. Otherwise, your selected brake fluid will get mixed with the moisture available in the old one, and it will lose its overall performance.

In short, brake fluid does not circulate or boil. This liquid gets pressurized and transmits force. If you try to circulate the brake fluid, it will make your whole braking system prone to heat damage. You cannot reuse the brake fluid or move it back to the master cylinder.  


Brake fluid is one of the most crucial liquids to have inside your vehicle. The primary purpose of this fluid is to keep the different braking components working smooth and offer a better braking experience. However, no two brake fluids are identical.

Before buying a high-quality brake fluid, you must do your research and find one that suits your budget and vehicle perfectly. DOT 5.1 brake fluids are at the top of the list for brake fluids. They have lower boiling points, meaning a better life span. 

Furthermore, it would help if you changed your brake fluid from time to time. As brake fluids can absorb moisture, an old one can make your whole vehicle prone to heat damage!