Can I use brake fluid DOT 5 with my new brake kit?

Brake fluid DOT 5: Before diving into brake fluid concepts, one obviously needs to have a basic understanding of what brake fluid actually is. An automotive braking system converts kinetic energy into heat in a bit to reduce vehicle momentum. In modern cars, brake fluid is used to create the pressure that makes the brake pads and rotors work.

Brake fluid is a type of hydraulic fluid that transfers force from the brake pedal to the brake caliper. The brake calipers then rub against the rotor to reduce momentum. Braking force is directly proportional to the force that the driver has exerted on the brake pedal or lever.

To have the perfect braking performance and response, it is very important to have the correct brake fluid. Having the wrong brake fluid could result in a longer stopping distance and even brake failure. In the worst case, the pedal could have free play and despite depressing the pedal all the way, the vehicle will not stop. Brake fluids are represented and categorized by their DOT classifications.

DOT stands for Department of Transportation, an agency that defines qualifications. DOT classifications can be simplified with three properties: chemical, boiling point, and moisture retention over time.


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Can I use DOT 5.1?

DOT 5.1 has very broad applicability and can be used with confidence in any brake system where the use of glycol ether fluid is specified. This includes state-of-the-art fully electric and hybrid electric vehicles where low conductivity is essential, as well as high-performance European vehicles. It is fully compatible and can replace or recharge systems that use DOT 4 and DOT 3 fluids.

Since DOT 4 and 5.1 are glycol-based brake fluids, they are compatible with each other, which means they can be easily mixed without damaging the system. of brakes. It is important to never confuse DOT 5.1 (glycol based) with DOT 5 which is silicone based and should never be mixed with any other DOT fluid. DOT 5 is used mostly in classic cars that remain in storage for long periods and need a brake fluid that does not absorb water.

Brake Fluid Comparison and Mixing

DOT 5.1 fluids are a development of DOT 4 which not only have higher boiling points (and retain them even better than DOT 4 in service) but also have a much better viscosity (thickness) at low temperatures. Part of the standards that DOT fluid manufacturers must meet are minimum dry and wet boiling points. These are the minimum temperatures your brake fluid must operate at before the brake fluid starts to boil, which can lead to complete brake failure.

The requirements for brake fluids are defined by some internationally recognized standardization organizations.

Can I use DOT 5 brake fluid with my new brake kit?

The owner of a 55′ Ford Sedan just sent us a note asking why we don’t recommend using DOT 5 brake fluid with our brake kits. Some of you are most likely asking the same question, so this post is designed to clear up the confusion around the different types of brake fluid.

If you head to your local auto parts store, you’ll see all kinds of brake fluids in the aisle. DOT 3 is always the most economical option: DOT 4 is approximately 50% more expensive than DOT 3 and DOT 5 is approximately twice as expensive as DOT 4. Some owners mistakenly assume that DOT 5’s higher cost equates to better performance , but this is not always the case. In fact, sometimes the exact opposite is true. To better understand why we don’t recommend DOT 5 for our brake kits, we need to take a crash course in chemistry.

Common brake fluids, such as DOT 3, 4, and 5.1, are mixtures of glycols and glycol ethers, while DOT 5 is silicone-based. DOT 3, 4 and 5.1 are hygroscopic, which is a fancy way of saying they absorb water. We know what you’re thinking: brake line moisture is bad! It’s true that we try to keep our brake systems “dry,” but over time, even a buttoned-up brake system with tight seals and fresh lines absorbs moisture. The key here is what happens to that moisture after it enters the system.

DOT 5 doesn’t absorb moisture, so some people think it’s the best option, but is it? Before you run to the parts counter, remember that while DOT 5 does not absorb water, it cannot/will not prevent moisture from entering the brake system. And since water is not absorbed by DOT 5, moisture builds up and causes localized corrosion within the brake system.

As fun as it sounds, DOT 3, 4, and 5.1 absorb moisture, which in turn eliminates puddling that can cause corrosion. More importantly, when brake fluid gets hot, the water trapped inside the brake lines (but not absorbed by the brake fluid) turns from a liquid to a vapor. Vapor is more easily compressed than liquid. With this in mind, imagine racing down the highway at high speed and hitting the brakes. When the hydraulic system sends DOT 5 fluid through a vapor pocket in the line, that pressure drop creates a soft pedal.

Know the Difference Between DOT3, DOT4, and DOT5 Brake Fluid

You rely on a good brake system to safely operate almost any powersports vehicle, and for that brake system to work properly, it must be maintained with the correct type of fluid. of brakes. Failure to maintain the brake system or the use of the wrong type of brake fluid could cause the brake system to deteriorate or even fail unexpectedly.

To understand brake fluid classifications, we have to mention what brake fluid does. Vehicles with hydraulic brakes (as opposed to cable-actuated brakes) use brake fluid to transfer force from a brake pedal or brake lever to the brake caliper or wheel cylinder, which converts the force into pressure. When the caliper or wheel cylinder puts pressure on the brake pad-rotor combination, or the brake shoe-drum combination, friction slows the vehicle down.

That friction creates heat, and that’s where brake fluid ratings come into play. The DOT (Department of Transportation) rating for a particular brake fluid represents its boiling point temperature in degrees Fahrenheit when dry or wet. Brake fluid with a DOT3 and DOT4 label contains glycol, which attracts water. 

Over time, it is normal for brake fluid to absorb a small amount of moisture from the atmosphere. The “wet” boiling point rating is the temperature at which brake fluid boils with a moisture level of about 4 percent. Because it is a fluid, brake fluid cannot be compressed; When you step on the pedal or squeeze the lever, almost all of that force is converted into stopping power. 

However, if there is water in the brake fluid and the brakes get hot enough to cause the moisture to boil, the moisture turns into a gas (vapour), which can be compressed. This can cause brake control to feel “mushy” and reduce braking performance. In an extreme case, the brake lever could go directly to the handlebars. Moisture in the brake system can also cause corrosion in brake calipers or brake cylinders, which can lead to brake fluid leaks and other inconvenient problems.

Keeping your brake fluid as “dry” as possible is the reason most vehicle manufacturers recommend changing your brake fluid on a regular schedule. Check your owner’s manual or consult a service professional for service intervals for your vehicle’s brake system. Your owner’s manual will also show you how and when to add brake fluid to the master cylinder reservoir.

That level can drop as new brake pads wear. Finally, your owner’s manual will tell you what type of brake fluid is compatible with your vehicle’s brake system. It is very important to use only that type of fluid when servicing the system or filling the reservoir. The specified fluid type is almost always stamped on the reservoir cap as well.

DOT3, DOT4 and DOT5 Brake Fluids Explained

There are three brake fluids available on the market for our general vehicles. The range increases in terms of performance in ascending order, which means that DOT3 is the most basic and DOT5 is the sophisticated one with richer substances. However, DOT4 is now the mainstream option on our regular vehicles.


DOT3 brake fluid is the most generic available on the market. DOT3 brake fluid typically contains about 80% glycol with other substances accounting for the remainder. DOT3 brake fluid is usually yellow in color. There are no safe standards for DOT3 or any other brake fluid, and boiling points vary from brand to brand. Simply put, DOT3 fluid typically has a dry boiling point of 205 degrees Celsius and a wet boiling point of 140 degrees Celsius. The wet boiling point is taken into account when the fluid has gained moisture over time. However, DOT3 gains less moisture with respect to time, over DOT4 fluid.

DOT4 brakes

DOT4 brake fluid is now used in most of our vehicles. It bridges the gap between DOT3 and DOT4 by offering the qualities of the other two fluids at an affordable cost. Talking about substances used, DOT4 brake fluid includes around 50-65% glycol ether base with around 20-40% borate ester base. DOT4 brake fluid has higher boiling points than DOT3, 230 degrees Celsius for dry and 155 degrees Celsius for wet. Speaking of properties, DOT4 gains moisture faster than DOT3 but has a high boiling point for both dry and wet conditions. Therefore, it offers more reliable stopping power but requires a faster fluid change.

DOT5 brakes

DOT5 brake fluid is used in high-grade vehicles that are primarily built to deal with high-intensity conditions. DOT5 is a fully synthetic silicone based brake fluid that does not contain moisture over time. Offers more compressibility than DOT3 and DOT4 brake fluids. DOT5 brake fluid also has a higher boiling point of 260 degrees Celsius dry and 180 degrees Celsius wet.

Because it does not contain moisture, it is the most reliable brake fluid and offers excellent braking performance with a longer replacement life. However, some brands now also offer fully synthetic DOT4 brake fluids that offer even higher boiling points than DOT5, making them more preferable for road use.

If you find this post about brake fluid DOT 5 helpful to you and you want to know more about car fluid knowledge, please check more on our website Auto Oil And Fluid. Thank you for your interest!


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