The Difference Between DOT 3, DOT 4 and DOT 5 Brake Fluid

Greetings, car enthusiasts! Dave here from First Place Auto Parts, and today we're tackling a common question we often receive: What brake fluid is right for your car or project? Whether you're installing a disc conversion kit or working on your brakes, choosing the correct brake fluid is crucial. In this video, we'll break down the differences between DOT 3, DOT 4, and DOT 5 brake fluids, helping you make an informed decision for your project.

🔍 *Understanding Brake Fluid:*
Brake fluids are classified by the Department of Transportation (DOT), and they come in varying types with distinct characteristics. Brake fluid is hygroscopic, meaning it absorbs moisture from the air. This moisture absorption affects the fluid's boiling point, a critical factor in hydraulic brake systems.

💡 *Why Brake Fluid Matters:*
Hydraulic brake systems rely on non-compressible fluid to activate components. The open caps on the master cylinder expose the system to atmospheric air, introducing moisture. Moisture in brake fluid can lead to vapor formation at high temperatures, resulting in a spongy brake pedal and decreased efficiency.

🌡️ *Boiling Points - Dry vs. Wet:*
Brake fluid specifications include dry boiling points (fresh fluid) and wet boiling points (after absorbing moisture). A brake fluid is considered compromised when it reaches 3.7% water content, emphasizing the importance of regular flushing.

🔧 *Types of Brake Fluid:*
1. *DOT 3:* Commonly used until the mid-'90s, DOT 3 has a dry boiling point of 401°F and a wet boiling point of 284°F. It's more susceptible to water absorption.

2. *DOT 4:* Similar to DOT 3 but with a higher boiling point. DOT 4 has a dry boiling point of 446°F and a wet boiling point of 311°F. It degrades less with water absorption.

3. *DOT 5:* Silicone-based, DOT 5 has a dry boiling point of 500°F and a wet boiling point of 356°F. It's suitable for high-performance applications but may result in a softer pedal feel.

👨‍🔧 *Choosing the Right Fluid:*
Consult your owner's manual or contact the manufacturer to determine the appropriate brake fluid for your specific application. Modern vehicles often use DOT 5 due to its higher boiling points.

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Until next time, keep the hammer down and stay between the guardrails! 🏎️💨

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