Rick CarltonModern automotive braking systems are hydraulically driven, using brake fluid. When you press the brake pedal, the fluid moves to create the force needed to bring your vehicle to a safe, controlled stop. But there is a lot more to know about brake fluid – let’s cover the basics.
What Is Brake Fluid For?
Brake fluid is the lifeblood of a braking system – nothing moves without it. It’s a incompressible hydraulic fluid that moves through the brake lines when you apply pressure to the brake pedal. This fluid transfers the pressure to the caliper pistons, which then drive the brake pads against the brake rotor. This creates the friction necessary to stop the wheels from turning.
What Types Of Vehicles Use Brake Fluid?
Virtually every vehicle on the road today relies on a hydraulic braking system. Common brake fluid types include DOT 3, DOT 4, DOT 5.1 (glycol-based), and DOT 5 (silicone-based). These are categorized by Department of Transportation (DOT) ratings, which determine the fluid’s boiling point and chemical makeup. DOT ranges include:
- DOT 3: The standard consumer grade fluid. It is glycol-based and suitable for most daily drivers, though it has the lowest boiling point.
- DOT 4: Designed for higher performance, DOT 4 features a higher boiling point than DOT 3, making it ideal for vehicles that experience hard braking for extended periods.
- DOT 5: A silicone-based fluid. Unlike glycol fluids, it does not damage paintwork, making it a favorite for vintage show cars. However, it is not compatible with ABS systems.
- DOT 5.1: A high-performance glycol-based fluid. It offers a high boiling point for use in performance vehicles and heavy-duty applications.
- EV-Specific Fluid: Electric Vehicles (EVs) use regenerative braking, so the mechanical brakes are used less often, which can lead to spot corrosion. That is why EV manufacturers recommend using brake fluids that feature advanced corrosion inhibitors.
Understanding and applying the proper fluid is critical to your vehicle’s safety and performance.
Can You Mix Different Types Of Brake Fluid?
Just because you can do something doesn’t mean you should. While DOT 3, 4, and 5.1 are technically compatible because they are glycol-based, mixing them can lower the overall boiling point and compromise the fluid’s integrity. Never mix DOT 5 (silicone-based) with any other type, as it will cause the fluid to thicken into a gel-like substance, leading to total brake failure. The short answer? Don’t do it.
What Does It Mean To Bleed The Brakes?
Hydraulic systems are designed to operate with no air in the lines or calipers. Bleeding is the process of purging air bubbles from the brake system. Air is compressible, whereas brake fluid is not; if air gets into your brake system, your brakes will feel spongy or unresponsive. Additionally, the ABS system will not work properly, and you may not get enough brake pressure in an emergency. The process of removing air from the brake system is called bleeding the brakes. There are several inexpensive pressure or vacuum bleeder tools available to make this easy.
Do I Need A Brake Fluid Flush?
A full brake fluid flush is only necessary when the fluid becomes contaminated or during major component replacements as there may be residual sludge in the sealed system. Over time, glycol-based fluid can absorb moisture (as it is hygroscopic), lowering the boiling point and causing internal rust in the braking system.
What Are The Signs Of Low Or Bad Brake Fluid?
If your fluid is low or has reached the end of its lifespan, there are a few symptoms that will alert you to this fact:
| Symptom | Potential Cause |
|---|---|
| Soft or Spongy Pedal | Air in the lines or moisture contamination. |
| ABS Warning Light | Low fluid level or a sensor detecting a drop. |
| Puddle Near Wheels | Clear/amber-colored oily leak = a line/seal failure. |
| Dark, Murky Fluid | Significant oxidation, moisture, or internal corrosion. |
| Burning Smell | Overheated fluid causing brake fade after heavy use. |
Remember that brake fluid is cheap, but the damage from neglecting it is not.
How Much Does Brake Fluid Cost?
Brake fluid itself is relatively inexpensive, typically ranging from $10 to $40 per liter depending on the DOT rating and brand. If you take your vehicle to a shop for a professional flush, expect to pay between $100 and $225 for labor and materials. Follow the chart below to find current pricing for our most popular brake fluids:
| Brand | Brake Fluid Type | Best For |
|---|---|---|
| Stoptech STR-600 | DOT 4 | High-performance street use |
| Stoptech STR-660 | DOT 4 | High-performance racing applications |
| Hawk Street | DOT 4 | Daily-driving applications |
| Brembo L04005 | DOT 4 | Mose suitable for vehicles with ABS |
| Brembo L05005 | DOT 5.1 | High-performance vehicles |
| Motul 100951 | DOT 5.1 | All types of hydraulically actuated systems |
| Wilwood Brake Fluid | DOT 5.1 | Designed for pro-level motorsports |
Can I Replace Brake Fluid Myself?
Replacing brake fluid is not a technically difficult DIY task, but it requires an understanding of the process and a few tools. To do the job, you’ll need a bleeder kit, and if your vehicle has a modern ABS system, it may require a specialized scan tool to cycle the valves during the bleed process.
When in doubt, trust a professional.
Where Should I Buy Brake Fluid?
Your braking system is a vitally important part of your vehicle, so certain to use reputable suppliers for replacement parts and service items. As the leading experts in stopping power, BuyBrakes.com offers:
- Massive Selection: From daily drivers to track-ready race cars, we stock the world’s top brands.
- Concierge Service: Not sure which DOT rating you need? Our free concierge team consists of brake experts ready to help you find the perfect match.
- Fast Shipping and Price Match: We get your parts to you quickly and guarantee the best price on the market.
Ready to upgrade your brake fluid and stopping power? Contact us with questions, and order online today!
