Do I need DOT 3 or DOT 4 brake fluid?
When it comes to maintaining your vehicle's braking system, the type of brake fluid you use is crucial. The two most common types of brake fluid are DOT 3 and DOT 4. Choosing the right one can be confusing, but this article will provide you with the information you need to make an informed decision.
What is the Difference Between DOT 3 and DOT 4 Brake Fluid?
The primary difference between DOT 3 and DOT 4 brake fluid lies in their boiling points. DOT 3 brake fluid has a lower boiling point, typically around 401°F (205°C) for the dry boiling point and 284°F (140°C) for the wet boiling point. DOT 4 brake fluid, on the other hand, has a higher boiling point, with a dry boiling point of around 446°F (230°C) and a wet boiling point of 311°F (155°C).
The higher boiling point of DOT 4 brake fluid makes it more resistant to heat, which is crucial in high-performance or heavily used braking systems. This is particularly important in vehicles that frequently tow heavy loads or engage in aggressive driving, as the brake fluid can become superheated, leading to a loss of braking power.
Which Brake Fluid Should I Use?
- For most passenger vehicles: DOT 3 brake fluid is generally sufficient, as it meets the minimum requirements for most standard braking systems.
- For high-performance or heavily used vehicles: DOT 4 brake fluid is the recommended choice, as it can better withstand the increased heat and pressure generated by more demanding braking systems.
- Always check your owner's manual: The manufacturer's recommendation should be your primary guide when selecting the appropriate brake fluid for your vehicle.
Regardless of which brake fluid you choose, it's essential to regularly check and replace it according to the manufacturer's recommended service intervals. Neglecting brake fluid maintenance can lead to a loss of braking performance and, in extreme cases, complete brake failure.
How do I know if I need DOT 3 or DOT 4 brake fluid?
Daily driving or commuting – DOT 3 is typically sufficient for light, everyday use where brake temperatures stay moderate. Towing, heavy loads, or mountainous driving – DOT 4 or DOT 5.1, with their higher boiling points, are better suited for these conditions to prevent brake fade.
Should I use DOT 3 or DOT 4?
DOT3 is an adequate brake fluid for use in later model vehicles, although it is rarely preferred. DOT4 fluid, for a slight increase in cost, will give significantly increased resistance to moisture absorption, thus decreasing the likelihood of corrosion compared to DOT3.
What happens if I put DOT 3 instead of DOT 4?
If you put DOT 3 brake fluid in a system that requires DOT 4, the main risk is reduced braking performance in high-heat situations because DOT 3 has a lower boiling point. While the fluids are compatible and mixing them is acceptable in a pinch, it's best to use the manufacturer-recommended fluid to ensure maximum brake safety, especially for high-performance or heavy-duty applications.
What happens
- Lower boiling point: DOT 3 has a lower boiling point (205∘C205 raised to the composed with power cap C205∘𝐶 dry, 140∘C140 raised to the composed with power cap C140∘𝐶 wet) compared to DOT 4 (230∘C230 raised to the composed with power cap C230∘𝐶 dry, 155∘C155 raised to the composed with power cap C155∘𝐶 wet).
- Potential for brake fade: In situations like descending a long, steep hill or aggressive driving, the brake fluid can get hot enough to boil. DOT 3 is more likely to reach its boiling point than DOT 4, which can cause a spongy brake pedal and loss of braking power (brake fade).
- Incompatibility with DOT 5: DOT 3 is not compatible with silicone-based DOT 5 fluid. Never mix DOT 3, 4, or 5.1 with DOT 5 fluid, as this can damage the brake system.
What to do
- Use the correct fluid: Always use the specific type of brake fluid recommended by your vehicle's manufacturer for safety and optimal performance.
- If you mixed them: If you've accidentally mixed the two, it's not an immediate emergency for normal driving, but it's recommended to have the system flushed and refilled with the correct DOT 4 fluid. This will ensure you have the higher temperature safety margin that was originally specified for your car.
- Wipe up spills: Brake fluid can damage paint. Be sure to wipe up any spills immediately.
What vehicles use DOT 4?
DOT 4 is used in some euro and domestic vehicles. DOT 4 Plus is used in Mercedes and Volvo. DOT 4 Low Viscosity is used in some BMW models. Finally, DOT 4 Racing usually has an added blue color.
