Even drivers who take good care of their vehicles often forget about the brake fluid. It’s generally not changed in short, frequent intervals like motor oil, although automakers do recommend changing it from time to time. Even though it is not changed on a regular monthly or mileage interval, it does need to be changed every two years. This is especially true with high performance vehicles or hard-working vehicles that put tremendous amounts of stress on their braking systems.

Brake fluid is used in your car as part of a hydraulic system, not primarily as a lubricant, so it does not get dirty as quickly as motor oil or transmission fluid. However, it gets dirty from normal use and does break down over time, reducing the performance of your braking system. This process is accelerated if you are particularly demanding of your brakes, but even if you always drive your vehicle gently, the brake fluid does need to be replaced occasionally.

One way to buy new brake fluid for your vehicle is to go to the dealership and purchase it from the manufacturer, but that isn’t always the most cost effective or convenient method. If you want to replace your brake fluid on a budget, you can buy brake fluid for just about any vehicle online, but there are many to consider. What factors should you consider when buying brake fluid? Do you need the pricier fluid or will the less expensive fluid work for your vehicle?

If you have never purchased brake fluid, we’ve picked the best options and explained the pros and cons for you below.

For more information on the best brake fluids, refer to our table of contents.

1. Editors Pick: Bosch ESI6 Brake Fluid

 Bosch ESI 6

If your vehicle uses DOT 3, DOT 4, or DOT 5.1 brake fluid, the Bosch ESI6 brake fluid will work for you. In most cases, brake fluids only apply to one of the DOT grades, but this fluid from Bosch applies to the vast majority of modern vehicles. That ability to use this fluid in so many different vehicles with different DOT grade requirements makes it a great choice for most drivers.

The “ESI” in the name stands for extended service interval, and that is the next key advantage of this fluid. Compared to traditional DOT 3 fluid, this Bosch fluid lasts 100 percent longer. It lasts 50 percent longer than traditional DOT 4 fluids and 10 percent longer than standard DOT 5.1 fluids. It’s also priced competitively for non-high performance brake fluid.

The Bosch ESI6 brake fluid has a dry boiling point of 518-degrees Fahrenheit and wet boiling point of 365 degrees, so it exceeds DOT 5.1 standards by 18-degrees dry and nine-degrees wet. Of course, the Bosch fluid offers dramatic increases over DOT 3 and DOT 4 fluids, so this Bosch fluid performs better when new and used than those standard lower-performance fluids. There is also some improvement over standard DOT 5.1 fluids, but the advantage isn’t as dramatic.

Finally, the Bosch ESI6 brake fluid has a recommended change interval of three years, while most standard brake fluids have a recommended change interval of two years.

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2. Prestone Synthetic Brake Fluid

Prestone Synthetic Brake Fluid

Prestone Synthetic brake fluid is offered for vehicles that need DOT 3 or DOT 4 brake fluid and it is one of the most cost-effective quality brake fluids available. While you will need to buy the grade that applies to your vehicle, the availability of DOT 3 and DOT 4 versions of this Prestone brake fluid makes this an great option for many drivers.

The Prestone Synthetic DOT 3 brake fluid has a dry boiling point (new, fresh fluid) of 460-degrees Fahrenheit  and a wet boiling point (used, with some water content) of 284 degrees. The DOT 3 requirements are 401-degrees dry and 284-degrees wet, so this Prestone fluid offers a reasonable performance improvement over standard fluids when new, but as it ages, it performs at the required level.

The DOT 4 version of this Prestone fluid has a dry boiling point of 510 degrees and a wet boiling point of 311 degrees. DOT 4 standards mandate a dry boiling point of 446 degrees and a wet boiling point of 311 degrees, so as is the case with the DOT 3, the Prestone product offers a significant improvement when new, but it loses quite a bit of its heat-handling abilities as it ages. 

3. Motul RBF 600 Synthetic Brake Fluid

Motul RBF 600 synthetic racing brake fluid is labeled DOT 4, but it will also work in vehicles that call for DOT 3. While it will work in average daily drivers, it is designed for the abuse that comes with road racing, so it can handle extreme heat loads. Also, when it is packaged, it is sealed with nitrogen, which increases shelf life by preventing contamination. 

Motul RBF 600 synthetic racing brake fluid has a dry boiling point of 594-degrees Fahrenheit and a wet boiling point of 399 degrees. That is a huge improvement over standard DOT 3 fluids with a dry boiling point of 401 and a wet boiling point of 284, but it also a big improvement over the standard DOT 4 boiling points of 446 dry and 311 wet. Again, “dry” is brake fluid fresh from the bottle while “wet” is when it has been used and absorbed some moisture from the atmosphere.

The Motul RBF 600 also serves as the best example of performance as brake fluid ages. It loses nearly 200 degrees worth of heat tolerance abilities when transitioning from dry to wet. Brake fluid is technically “wet” when it has a water-by-volume content of 3.7 percent, and with that minor amount of moisture, this high performance brake fluid on our list declines in performance by roughly a third while lesser fluids decline by greater margins.

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4. Castrol SRF Racing Brake Fluid

 Castrol SRF

Castrol SRF synthetic racing brake fluid is another high performance option on our list and it is also one of the most expensive. This fluid is engineered to replace DOT 3 and DOT 4 fluids, but it offers boiling protection levels far beyond that of standard DOT 3, DOT 4, and DOT 5.1 brake fluids. This fluid is intended for high performance use, offering superior protection during the toughest forms of racing, but it will also work in your daily driver or your work truck. In addition to offering excellent protection against boiling under stress, it also stands up better to contaminants, losing just a small amount of boiling protection as it acquires water content.

When the Castrol SRF synthetic racing brake fluid is new, it has a boiling point of 590-degrees Fahrenheit. That is an advantage of 189 degrees over DOT 3, 144 degrees over DOT 4, and 90 degrees over DOT 5 grades. More importantly, when the Castrol SRF fluid reaches the “wet” point with 3.7-percent water-by-volume, the boiling point only drops to 518-degrees Fahrenheit. DOT 5 brake fluid grades have the highest “wet” standard boiling point of 356 degrees, so when the Castrol fluid has been broken in a bit, it continues to exceed the “dry” requirements of standard DOT 3, DOT 4, and DOT 5 fluids by a considerable margin.

This ability to maintain an extremely high boiling point when water content climbs makes this one of the best performing brake fluids on our list.

5. ATE TYP 200 Brake Fluid

If you are looking for a combination of performance and affordability, ATE TYP 200 racing brake fluid is a great option. This is technically a DOT 4 fluid, but it comfortably exceeds DOT 3 and DOT 4 requirements. It costs less than most other high performance fluids while offering similar improvements over standard brake fluids.

The ATE TYP 200 racing brake fluid has a dry boiling point of 536 degrees and a wet boiling point of 374 degrees. With DOT 3 rated at 401/284 degrees, DOT 4 rated at 446/311 degrees, and DOT 5 rated at 500/356 degrees, this ATE exceeds the requirements for every grade of standard brake fluid. It offers a huge improvement in performance over standard DOT 3 or DOT 4 brake fluids while only costing a little more than non-performance options.

If you are looking for a brake fluid that offers substantially greater resistance against boiling, but you don’t want to spend a ton of money, the ATE TYP 200 is one of the best options on the market. It is less costly than other racing brake fluids, but it offers similar boiling points, making it ideal for performance settings.

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How Brake Fluid Works

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When you push the brake pedal in your vehicle, the power brake system forces brake fluid through all of the lines and into the braking assemblies behind each wheel. In vehicles with disc brakes, the brake fluid pushes the pistons in the calipers out against the brake pads, which then clamp down on the rotors. In a vehicle with drum brakes, the brake fluid causes the wheel cylinders to push out against one end of the brake shoes, pushing them out against the brake drum. When you release the brake pedal, that fluid pressure in the brake calipers or wheel cylinders drops as the fluid moves back into the lines.

The problem with brake fluid is that it is hygroscopic, which means that it naturally absorbs moisture from the air. That moisture turns into water in the brake fluid. That water is the difference between dry and wet brake fluid. Dry fluid is new, fresh out of the bottle. Brake fluid is considered to be wet when it reaches a water-by-volume level of 3.7 percent. As you might imagine, water has a lower boiling point than the brake fluid, so as water mixes in the brake lines with the brake fluid, the boiling point of the brake fluid is reduced.

That boiling is the biggest risk for the performance of brake fluid. During the braking process, a tremendous amount of heat is transferred from the pads or shoes into the brake fluid. Modern anti-lock braking systems and traction control systems also add heat, and all of this heat is what causes the brake fluid to boil. When it boils, vapor builds up around the braking assemblies at the wheels, greatly reducing braking performance. Boiling breaks down the fluid, leading to a greater decline in performance and a gradually lowered boiling point.

As your brake fluid gets older and absorbs more water, it is more likely to reach the point of boiling more often, which increases the rate at which the fluid breaks down. That is why you have to change your brake fluid every couple of years, as the fluid continues to break down and absorb water as it ages, continuing to negatively impact performance.

You can regain proper braking performance with new brake fluid, but changing your brake fluid isn’t as simple as changing your oil. Your brake fluid needs to be drawn from the system with a vacuum-based tool that you can purchase anywhere that sells brake fluid. However, with one of these relatively inexpensive tools and the proper brake fluid, you can restore or even improve the performance of your vehicle’s braking system.

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