Are you thinking of topping off the DOT 3 with the DOT 5 brake fluid? If this is the case, then you need to read this article first because the switch will not be that smooth after all and you could face a ton of issues.
Having to choose a brake fluid is not as easy as you probably think because there are more than a few of them and this could be a big challenge for you as a car owner because choosing the right one will be a big headache in some cases.
This is why you need to investigate things deeper and learn more about the positives and negatives of all these fluids and see which one is the best for your car. You just don’t want to make the wrong decision and add the wrong fluid into your braking system on your car. And we are going to help you out with that in this article.
First, we are going to learn what is the DOT abbreviation and what it means. Then we will go through all of the different types of DOT fluids and then focus primarily on the DOT 5 brake fluid where we will list all the positives and negatives of running this fluid and why you should or should not run this brake fluid on your car. Then we will learn how to convert your brake fluid from DOT 3 To DOT 5 fluid on your car. So, if you want to learn more, please follow along.
What Is DOT Brake Fluid?
Before we dive into more complex topics such as the DOT 5 brake fluid, let’s first take a look at the basics of the brake fluid and also learn what this DOT abbreviation means in the first place. Knowing this will be a good starting point for beginners who are not into cars and want to learn the basic stuff.
So, what is brake fluid in general? The brake fluid is simply a hydraulic fluid that is used for brake system applications.
This means that it is rather different from the regular hydraulic fluid that is known as ATF or transmission fluid.
But still, the core of this type of fluid is rather the same. The only difference is the color as well as some characteristics of this specific fluid that allows it to withstand more pressure and deliver good performance under extreme heat. Because brakes are getting really hot under heavy braking and even in normal use.
But what does the DOT means? Well, this is only an abbreviation for the Department of Transportation. This is the institution that standardizes these types of fluids and makes them a standard on cars.
What is worth noting is that even though the DOT is an American institution, these standards are global and used all over the world. So, in most countries where you travel, you will come across DOT 4, DOT 5 brake fluid, and other types that we are going to list in the following chapters more in-depth.
Another thing to add is that all the types of fluids are rather the same by structure except the DOT 5 brake fluid. And later on in this article, we are going to explain why is this the case and how they differentiate.
Types Of Brake Fluid?
Now as we cleared the basics of the DOT brake fluid and learned what this type of fluid is in the first place.
We think that now it is time to cover some of the types of DOT brake fluids and one of them is the DOT 5 brake fluid. In the following chapters, we will cover briefly the characteristics of all of these fluids and learn more about what is different among them and then we will solely focus on the DOT 5 brake fluid and its pros and cons. So, if you want to learn more, please follow along.
DOT 3 Brake Fluid
Now let’s begin with the DOT 3 brake fluid. This type of fluid is one of the most common brake fluids used out there and it is worth noting that this type of fluid is mainly used on older vehicles that are not reached the DOT 4 standard. The DOT 3 is equivalent to the SAE J1703 standard.
The DOT 3 is a glycol-based type of fluid and is backward compatible with the DOT 4 and DOT 5.1. But is not compatible with DOT 5 brake fluid, why is the case we are going to explain later on in this article.
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It is worth noting that this type of fluid starts to boil at the lowest temperature of any type of brake fluid out there. More precisely the dry boiling point is at about 401 degrees Fahrenheit while the wet boiling point is at about 284 degrees Fahrenheit.
The thing to note is that the dry boiling temperature is the temperature when we consider using DOT 3 from a new container. Meaning that this fluid is totally fresh. While the wet boiling temperatures are when this fluid is diluted with water.
And this process occurs over a long time of use and abuse. So, if you haven’t flushed your fluid for a long time, then you have probably a low wet boiling temperature and your brakes will not perform in heavy-duty use as they should.
Overall, using this type of brake fluid is not a good idea if you want to apply it on some heavy-duty applications because of its low boiling temperature.
DOT 4 Brake Fluid
Now let’s cover the next type of brake fluid which is the DOT 4 type of brake fluid. The DOT 4 brake fluid is a slight improvement over the DOT 3 but not as such as the DOT 5 brake fluid.
What is different when it comes to the DOT 4 in comparison to the DOT 3 is the improved formula.
This improvement formula does not only contain ether glycol compound but also contains borate esters. This greatly improves the performance of this fluid and also allows it to run at really hot temperatures.
The DOT 4 has a dry boiling temperature of 446 degrees Fahrenheit while the wet boiling temperature is 311 degrees Fahrenheit. This is a big improvement over the previous designs that have really poor performance on different temperatures and the DOT 4 can be used on heavy-duty applications.
What is good is that the DOT 4 is interchangeable when it comes to mixing with the DOT 3 since they are both glycol-based solutions.
But still, you should not mix them together. When it comes to switching from DOT 3 to DOT 4 we would recommend you do perform a complete flush of the system and add completely new fluid.
This way you will get the best performance from the fluid when it comes to the dry boiling point temperature which will be 446 degrees when it comes to installing a new fluid, while if you mix it, you will only get a wet boiling point performance of 311 degrees which is not that good after all.
But what about the DOT 5 brake fluid? From what compounds is this fluid made and in what ways it is different from the previous iterations? Let’s elaborate more on that next.
DOT 5 Silicone Brake Fluid
Now let’s discuss the DOT 5 brake fluid, how the DOT 5 is different in comparison to other types of brake fluids that are out there?
The first thing that you will notice is the DOT 5 brake fluid color. The color of the DOT 5 brake fluid is purple. Unlike the glycol-based fluids which are usually clear in color and don’t have any coloring to them.
And this is for a reason, the DOT 5 is a silicone brake fluid. This means that it is not produced from the same compounds as the DOT 3 and DOT 4.
It has a completely different chemical structure since it’s made out of silicone and it does not resemble the glycol-based compounds in any way possible. This is why manufacturers gave it a distinctive purple color to make it different so people would not mix these two types of fluid.
Another interesting thing about the DOT 5 fluid is that it does not absorb water. Glycol-based fluids can be diluted with water but the DOT 5 simply cannot be diluted at all.
In addition to this, the car needs to have a DOT 5 brake fluid compatibility. This means that it should be designed from the factory to work with this type of fluid. And this created a big burden when it came to its adoption.
What this fluid exceeds is the dry boiling point which is at about 500 degrees and the wet boiling point which is at about 356 degrees. This is why it is used on a lot of racing applications that need this heat resistance and ability to deliver the performance when needed.
DOT 5.1 Brake Fluid
Now let’s cover the last type of brake fluid which is the DOT 5.1 brake fluid. But why is this fluid called 5.1, is this some kind of an update to the DOT 5 brake fluid? Well, actually no.
This type of fluid is different in a lot of things in comparison to the DOT 5. Namely, it is different in its structure.
Because of the slow adoption of the DOT 5, something had to be done. A ton of carmakers didn’t want to swap to this type of brake fluid so there needed something to be done.
More precisely to use the good old glycol borate ester formula from the previous generations but to make it better and perform as the DOT 5 brake fluid.
So, that’s how the 5.1 was born. This fluid is compatible with all the previous fluids like the 3 and 4 but not with the DOT 5.
Still, though, it has the same temperature characteristics as the DOT 5. This means that it has a dry boiling point of about 500 degrees Fahrenheit and a wet boiling point of 356 degrees Fahrenheit. Which is a good improvement over the old designs such as the DOT 3 and 4. But what about the DOT 5 brake fluid, what are its pros and cons? Well, that’s what we are going to cover next.
Pros & Cons Of Dot 5 Brake Fluid
Now let’s cover some of the pros and cons of the DOT 5. Knowing these things is really important to determine if you want this type of fluid on your car.
Since a lot of people are confused by the numbers and could easily go for a DOT 5 and ruin their braking system completely. So, what are the pros and cons of running DOT 5 in your car? Let’s elaborate on them in the following two chapters.
Pros
Now let’s first discuss more on the pros side of things. What are the benefits that you will get if you are running this type of fluid on your car?
Well, when it comes to pros, it is worth mentioning that this DOT 5 brake fluid basically outperforms anything out there when it comes to the temperatures that could withstand. The boiling point of DOT 5 brake fluid is really high at up to 500 degrees.
This means that this type of fluid is very friendly when it comes to using it in racing applications and other applications that are demanding and require the brakes to run at really high temperatures.
So, if you are planning to use this fluid for racing and other high demanding situations, it will be the way to go if you want the best for your car.
Another pro for the DOT 5 brake fluid is that it does not mix with water. This means that it is less corrosive to your braking system and will not create rust buildup on the brake lines and inside the calipers. This means less dirty brake fluid compared to when using the glycol-based solutions.
But there are also a ton of drawbacks that this fluid has if you didn’t know. So, what are these drawbacks? Let’s elaborate on them next.
Cons
Now let’s discuss the cons of DOT 5 brake fluid. And frankly, there is a lot to talk about when it comes to the cons of this type of fluid.
The first and biggest con when it comes to this fluid is that it cannot run on any type of brake system. It means that this fluid can only be used on brake systems that have DOT 5 brake fluid compatibility.
Another con when it comes to this type of fluid is that it cannot be mixed with glycol-based fluids because it will not mix with them and also not deliver the performance you desire when you do so on your car.
The next thing is that it is not that compatible with ABS systems. It could cause a malfunction in the ABS system because it traps the air. And frankly, you don’t want to have air in your system when the ABS needs to engage. This means even a small leak of air could ruin the performance of this type of fluid in your car and prevent the ABS from working right.
The next con when it comes to the drawbacks is the price. This type of brake fluid on average is about three times more expensive than your regular DOT 3 fluid and this is the most important reason why DOT 5.1 was invented and the DOT 5 brake fluid hasn’t become the mainstream when it comes to car applications. But what is the difference between the two? Well, that’s what we will cover next.
Difference Between DOT 3 And DOT 5 Brake Fluid
And what about the difference between DOT 3 and DOT 5 brake fluid? What is different between the two fluids and what are the pros and cons of each one?
DOT 3 as we mentioned is a glycol-based type of fluid. It has a much lower heat resistance temperature and is old technology. In terms of performance under heavy use and abuse it is quite poor and you should definitely switch on a DOT 5.1 fluid if you want to get something better performing and something that will deliver a lot. And what is good when it comes to these two types of fluids is that they are really interchangeable. You can flush the old DOT 3 and replace it with 5.1.
While on the other hand DOT 3 is not interchangeable with DOT 5 brake fluid. These two are completely different and do not overlap. So, if your car is not certified for DOT 5, you should avoid using it and instead use the 5.1 fluid instead. This will guarantee that you get the best performance for your money.
But when it comes to the performance 5 has a ton of positives in comparison to the DOT 3. This type of fluid is basically a ton better than the 3 and will work on any conditions out there and deliver the performance that you need. But what about changing from DOT 3 to DOT 5 brake fluid? Let’s elaborate more on that next.
Changing From DOT 3 To DOT 5 Brake Fluid
When it comes to changing from one to another fluid we would not recommend you to do so. Even though it is possible to do this type of work on your car.
How you can do this type of work on your car? Well, you will have to flush all the lines first and remove the DOT 3 first.
The second thing that you will want to do is to flush all the brake lines again with 100% denatured alcohol. But before you run the alcohol, you will have to remove all the rubber parts in the calipers and master cylinder. This is the case so the alcohol doesn’t harm these components.
Then you can connect everything and run your car with the DOT 5 brake fluid. This is a long procedure so you should think twice before you decide on this step. Since you can just get a DOT 5.1 which performs almost the same as the 5.
Conclusion
In this article, we have covered quite a bit when it comes to the DOT 5 brake fluid. First, we learned what this DOT means in the first place and then we covered all the types of fluids and their characteristics.
Then we learned more about the pros and cons of the DOT 5 and how it outperforms other fluids as well as the comparison with the DOT 3.
F.A.Q
Now let’s answer some frequently asked questions.
What Is DOT 5 Brake Fluid Used For
DOT 5 is mainly used for classic cars. Since they do not run ABS and it is a really good application for these types of vehicles. In addition to this, this type of fluid prevents rust in the brake lines and this makes it perfect for cars intended for long-term storage. So, if you have a classic motor, this is the right fluid for you.
What Vehicles Use DOT 5 Brake Fluid
Vehicles that do not have ABS systems as well as classic motors that are intended for long-term storage. The reason for this is that the DOT 5 does not work well with ABS systems and the reason two is that it doesn’t cause rust. So, running this fluid for a car that is intended for storage is perfect.
What Color Is DOT 5 Brake Fluid
This fluid is purple in color. Unlike other brake fluids which are clear in color. This way you will never mix them and possibly ruin the braking system on your car.
Can You Mix DOT 3 And DOT 5 Brake Fluid
No, you cannot mix the two. Mainly because they are two different fluids that are not intended to be mixed. They have different chemical formulas and any mixing will create more damage than good. So, you should never do that.
Where To Buy DOT 5 Brake Fluid
You can buy this fluid anywhere, online, at your local parts store, or anywhere where there is a good option for brake fluids you will be able to get this type of fluid as well.
Is DOT 5 Brake Fluid Compatible With DOT 3
No, it is not compatible. The first one is a silicone-based solution while the latter one is a glycol-based solution. This means that mixing them is out of the question and they will not work together.
