In this guide, we are going to consider the differences between Dot3 vs Dot4 brake fluid, so you know which is better.
The topic of brake fluid isn’t well-understood. We all know our vehicles require it, but that doesn’t mean we understand what it does or what the letters and numbers for each type of brake fluid signify. Some individuals are unaware that brake fluid has varying ratings, which might affect how well their vehicle operates. Do you know the difference between DOT 3 and DOT 4 brake fluid, for example? The majority of car owners do not.
Understanding what brake fluid does, what the ratings represent, and the differences between various types of brake fluids will help you make smarter decisions about your car’s braking system’s long-term care and maintenance.
Dot3 vs Dot4 Brake Fluid
When comparing the two, keep in mind that, because there is no standard formula for brake fluids and each type of brake fluid may contain various compounds or chemicals, there are only a few distinctions between DOT 3 and DOT 4 brake fluid.
The Primary differences between Dot3 and Dot4 brake fluid are as follows:
- DOT 3 brake fluid absorbs less water than DOT 4 from the air over time, meaning you’ll need to have your fluid changed less frequently.
- DOT 4 brake fluid has higher dry and wet boiling points, making it safer for higher temperatures.
Finally, the ability to tolerate heat and water absorption is the difference between DOT 3 and DOT 4 braking fluids. When it’s time to replace your brake fluid, check your owner’s handbook to learn what type of brake fluid your vehicle requires. You should never mix various types of brake fluid since incompatibility can cause your brakes to fail.
Dot3 vs Dot4 Brake Fluid Ratings
Let’s now look at the Dot3 and Dot4 brake fluid ratings and what they do…
The figures are based on the boiling point of your braking fluid. There are two different types of boiling points. The boiling point of a fluid that hasn’t been contaminated with water or other impurities is called the dry boiling point. The boiling point of a fluid that contains water is called the wet boiling point. DOT 3 or DOT 4 brake fluid has traditionally been used. The Department of Transportation (DOT) is the organization that determines the ratings.
When comparing DOT 3 and DOT 4, the dry boiling point of DOT 3 braking fluid is 401 degrees Fahrenheit, and the wet boiling point is 284 degrees Fahrenheit. Because most brake fluids do not have a standard formula, this is an estimated boiling point, and the exact boiling points may vary. These levels are easily exceeded by typical DOT 3 fluids. One of the elements that contribute to water absorption is the presence of an 80 percent glycol ether basis in DOT 3 fluid.
DOT 4 fluids have greater dry and wet boil points, which are necessary in brake systems that generate more heat as a result of higher speeds, heavier towing loads, and other factors. DOT 4 brake fluid absorbs moisture more quickly than DOT 3 brake fluid, hence it should be replaced more frequently.
DOT 4 fluid normally has 50 to 65 percent glycol ether base with 20-30 percent Borate Ester, which helps the fluid withstand boiling. If your DOT 3 fluid contains 3.7 percent moisture, it will boil at around 290°F. At 330°F, the same amount of moisture in your DOT 4 Brake Fluid will boil. The DOT 4 fluid absorbs the 3.7 percent water 20 percent faster than the DOT 3 fluid.
The boiling point and longevity of DOT 3 vs. DOT 4 brake fluid are the most noteworthy differences between the two varieties. DOT 4 brake fluid requires more frequent replacement than DOT 3.
DOT 5 and DOT 5.1 brake fluid classifications are also available, however these types of brake fluid are significantly less prevalent. DOT 5 contains silicone, however DOT 5.1 contains less than 70% silicone, making it more compatible with other braking systems than DOT 5, which is incompatible with anti-lock brakes and fluid grades 3 and 4.
DOT 5.1 brake fluid is compatible with DOT 3 or DOT 4 brake fluid and is made up of 20-30% Glycol Ether and 50-70 percent Borate Ester. However, you should always use brake fluid with the same rating as the manufacturer’s recommendation in your vehicle’s owner’s handbook.
How Does Brake Fluid Work?
Hydraulic braking is used in the majority of automobiles. When you apply pressure to the brake pedal, braking fluid is sent to your calipers, which press the pads against the rotors. The pads and rotors will generate more friction as you apply more pressure, and the automobile will come to a faster halt.
You won’t be able to stop without brake fluid. You should also change your brake fluid on a regular basis because it degrades over time. It has the ability to absorb moisture, which can cause your brakes to fail. Bad braking fluid can lead to brake system failure, which can be fatal. Finally, keeping your brake fluid up to date is critical for safe driving.
It’s simple to understand why moisture is so detrimental for the fluid. The boiling point of fresh brake fluid is higher than the temperature produced during braking. Water, on the other hand, has a significantly lower boiling point and can boil as a result of the high temperatures generated during braking.
Moisture absorbed by the braking fluid has the potential to boil, generating gas. When you press the brake pedal, the gas in your braking system compresses rather than forcing the brake fluid to your rotors. Simply put, boiling brake fluid may cause you to hit the brakes and the pedal to drop to the floor without slowing the vehicle. This is why it’s critical to replace your brake fluid on a regular basis.
Can Dot3 Be Used Instead of Dot4?
Yes, DOT 3 and DOT 4 brake fluids are interchangeable. DOT 4, on the other hand, has a greater boiling point. It is incompatible with other brake fluids and is mostly used in historic cars that are stored for extended periods of time and require a brake fluid that does not absorb water.
Can Dot3 and Dot4 Brake Fluid Be Mixed?
Because DOT 4 and 5.1 are both glycol-based brake fluids, they are compatible with one another and can be mixed without causing damage to your brake system. The worst thing that can happen if you mix DOT 3, 4, and 5.1 brake fluids, providing it’s new, is a drop in the boiling point of the entire fluid.
What Happens If You Use The Wrong Brake Fluid?
The use of the incorrect fluid can result in inadequate lubrication, overheating, and transmission failure. Even if the transmission is flushed, a mechanic may not be able to reverse the damage. Inadvertently adding engine oil or brake fluid to your transmission might potentially cause it to fail.
Can Dot5 Replace Dot3 Brake Fluid?
DOT 5 can be used to enhance or replace DOT 3 and 4, but it should never be mixed with any of the other fluids. In terms of boiling point and viscosity, this fluid is identical to DOT 5 silicone; nevertheless, it is also compatible with polyglycol-based systems and anti-lock brakes.
Can I mix Old and New Brake Fluids?
One of the reasons you refill brake fluid is because it is prone to absorbing water. You CANNOT use the same fluid twice, and you CANNOT combine old and new fluids.
Is Dot3 Brake Fluid Same As Power Steering Fluid?
Brake fluid and power steering fluid are not interchangeable since they were conceived and improved for quite different purposes within automobiles over time. Putting brake fluid in your power steering reservoir will do more than just reduce the performance of your power steering.
Hope you now know the differences between Dot3 vs Dot4 brake fluid? If you still don’t understand, do well to ask your mechanic for more explanation and advise and which one you should go for.