The brake fluid helps move the important components of the braking system when we press the brake pedal. It ensures that your vehicle comes to a stop when you need it to. So it is absolutely necessary to use the best brake fluid for the braking system.
And when we think about it, two of the most common types of brake fluid that pop up in front of our eyes are DOT 3 and DOT 4. They might look similar, but what are the differences between DOT 3 and DOT 4?
DOT 3 and DOT 4 are both glycol-based. But there are some dissimilarities in the aspects of compatibility, boiling points, cost, composition, etc.
Here, I’ll give you an overview of the two brake fluids, their pros and cons, key differences, and other related important things. Let’s Go!
Overview of DOT 3
DOT 3 brake fluid is a type of glycol-based brake fluid that has been used in vehicles for decades. It is more common to us because it is compatible with most types of brake systems.
Also, most of the vehicle manufacturers recommend it too.
This fluid has a yellow color and is hygroscopic. It means that it will absorb moisture from the air. So, once you open the container, you should use it right away.
Thinking about the boiling point? According to the Department of Transportation (DOT) standards, boiling point of DOT 3 brake fluid is a minimum of 401°F (205°C) for dry boiling point and a minimum of 284°F (140°C) for wet boiling point.
This boiling point is comparatively lower to DOT 4 and DOT 5.1. That is why if it absorbs moisture the boiling point will go lower and it will lose its effectiveness in the extreme driving conditions.
One of the best things I love about DOT 3 brake fluid is it’s typically less expensive. You can find it at most of the auto parts stores and repair shops.
So if you don’t use a heavy-duty vehicle and brake aggressively, this brake fluid should do the job for you.
Minimum DOT standards are ensured
Can be used in most vehicles
|Comparatively lower boiling point
Not ideal heavy-duty vehicles
Overview of DOT 4
DOT 4 brake fluid is also a glycol-based brake fluid. It is kind of similar to DOT 3 brake fluid in many ways, but has some key differences.
This brake fluid has a light yellow color. It’s less hygroscopic compared to the previous one. So it will absorb less moisture from the air.
However, the major difference is the boiling point. As per Department of Transportation (DOT) standards, the minimum boiling point requirements for DOT 4 brake fluid are:
- Dry boiling point: 230°C (446°F) or higher
- Wet boiling point: 155°C (311°F) or higher
As you can see it is quite higher than DOT 3. So this fluid can provide better resistance.
But although it absorbs less moisture and has a higher boiling point, you should still use it as soon as the container is opened.
DOT 4 is compatible with high-performance vehicles. So, if you drive a heavy-duty automobile or drive in rough conditions this can be your choice.
|Comparatively higher boiling point
Compatible with high-performance vehicles
Suitable for extreme driving conditions
May not be compatible with older vehicles
Dot 3 vs Dot 4 Brake Fluid: 6 Key Differences You Need to Know
Hope you got a good brief idea about both of them. Now, there are some key differences that separate these two. Check them out.
|1. Boiling Point
|Dry Boiling point: 205°C/401°F
Wet Boiling Point: 140°C/284°F
|Dry Boiling point: 230°C/446°FWet Boiling Point: 155°C/311°F
|2.Compatibility with Vehicles
|4. Moisture Resistance
|Glycol Ether/Borate Ester
1. Boiling Point
This is the major difference between the two. You already know their boiling points from the above chart I believe.
DOT 3 brake fluid has a lower boiling point and is typically used in standard vehicles. It is suitable for most of the older cars too because it can be properly utilized in the older braking systems.
If you are doing heavy braking with DOT 3 then it can easily boil. What happens then? It can lead to a loss of braking effectiveness.
So, most of the experts do not recommend it for heavy-duty applications.
On the other hand, DOT 4 brake fluid typically has a higher boiling point compared to DOT 3 brake fluid. So it won’t boil that easily. You can be safe while driving high-performance vehicles and driving in extreme conditions.
2. Compatibility with Vehicles
DOT 3 brake fluid is actually recommended for standard vehicles. That too with regular driving conditions.
It is because most of the normal standard cars do not require too much power to stop the car. They are not even driven aggressively by us either. That is why this Glycol-based fluid is suitable for the standard cars.
Now let’s talk about DOT 4. It is designed to meet the demands of extreme driving conditions. Racing cars, police cars, and heavy-duty vehicles need to brake aggressively quite often.
Another thing is, these cars are driven in extreme conditions as well. Therefore they use DOT 4.
DOT 4 brake fluid generally offers higher performance characteristics compared to DOT 3 brake fluid.
The DOT 3 brake fluid easily absorbs water. That’s why when we brake heavily it breaks down.
But during high temperatures or braking aggressively continuously, DOT 4 does not break down easily. No wonder why they are recommended for heavy-duty automobiles.
4. Moisture Resistance
As you know already, both DOT 3 and DOT 4 brake fluids are hygroscopic. Which means they both can absorb moisture from the air over time. But there is a difference in the resistance ability.
DOT 4 brake fluid generally has better resistance to moisture absorption compared to DOT 3 brake fluid.
As much moisture the brake fluid absorbs, the boiling point decreases. So it is another important difference between the two.
DOT 3 consists of glycol and ether. It is enough to tackle the normal driving conditions and suitable for average economy cars.
On the contrary, glycol ether and borate ester are used in DOT 4. They can handle hard driving conditions.
DOT 3 brake fluid is less expensive compared to its later version. It is widely available too.
Because the higher performance characteristics and higher boiling point of DOT 4 brake fluid results in a higher cost compared to DOT 3 brake fluid.
Can you mix DOT 3 and DOT 4 Brake Fluid?
Yes, you can. As they are both Glycol based, you can mix them without worrying.
DOT 3 and DOT 4 are compatible with one another. So, if you are using DOT 3, you can mix it up with DOT 4.
As a matter of fact, one of my friends used DOT 3 for a couple of years. But when he had to drive in a hilly area he quickly shifted to DOT 4. And guess what?
Everything was perfectly fine.
But here’s another thing. You already know that DOT 4 has a higher boiling point. So, if your manufacturer says to use DOT 4 from the beginning, it is not wise to use the DOT 3. At least I won’t suggest that you do that.
Because when you suddenly use a brake fluid with less boiling point the performance is likely to decrease. That is why if you are driving in an extreme condition, try to keep using the DOT 4.
ONE MORE THING! These two can be mixed because they are both Glycol based. But a lot of people mix them up with DOT 5. NEVER DO IT!
DOT 5 is silicone based. It doesn’t absorb water from the air and is not compatible with the previous two brake fluids. So if you mix either DOT 3 or DOT 4 with DOT 5 even brake failure might happen. Try to avoid it.
How Often Should Brake Fluid be Changed?
It is recommended that you should change your brake fluid every 2 years no matter what the mileage is.
The best way to find it out is your manufacturer’s recommendation. Check it and you will get the best idea.
My suggestion would be to try to change it a bit earlier. In the span of every 1 to 2 years and in around every 30000 miles.
This should help to keep the braking system in the best possible shape.
DOT 3 or DOT 4 – Which one should you use?
Well, it depends on your vehicle and driving condition.
If you use a normal car and don’t have to perform aggressive braking then you should use DOT 3.
But if you use a heavy-duty vehicle or racing car or have to perform hard braking, then DOT 4 should be your choice.
You should always check the owner’s manual or follow the manufacturer’s recommendation. That is the best thing to do!
Frequently Asked Questions
Q. Can you mix DOT 5.1 with DOT 3 and DOT 4?
Answer: Yes, Certainly! You can mix DOT 5.1 with DOT 3 and DOT 4. But never mix any of them with DOT 5.
Q. What’s the average brake fluid cost?
Answer: On average, it can be from $80 to $130. Usually cars need a quart of brake fluid. It will cost you just around $10-$20 bucks. And the labor cost can be anywhere from $70 to $100.
I hope that you have made up your mind on DOT 3 vs. DOT 4. Both of them have made a name for themselves in the market and help to assist the braking system effectively.
It just depends on your very own personal vehicle and your driving conditions. I hope you will choose the most suitable one.
Till then, safe driving!