Does it matter what dot brake fluid you use?
The short answer is yes, it does matter what dot brake fluid you use in your vehicle. The dot number of the brake fluid refers to its boiling point and compatibility with your car's brake system. Using the wrong dot brake fluid can lead to serious safety issues and damage to your brakes.
Understanding Dot Brake Fluid
Brake fluid is a critical component of your vehicle's braking system. It is responsible for transmitting the force from the brake pedal to the brake calipers, causing the pads to press against the rotors and slow or stop the car. Brake fluid must be able to withstand high temperatures without boiling, as this can lead to a spongy or unresponsive brake pedal.
The "dot" number of brake fluid refers to its boiling point. The higher the dot number, the higher the boiling point of the fluid. The most common dot ratings are:
- DOT 3 - Boiling point of 401°F (205°C) dry, 284°F (140°C) wet
- DOT 4 - Boiling point of 446°F (230°C) dry, 311°F (155°C) wet
- DOT 5 - Boiling point of 500°F (260°C) dry, 356°F (180°C) wet
- DOT 5.1 - Boiling point of 518°F (270°C) dry, 356°F (180°C) wet
The wet boiling point is the temperature at which the fluid will boil after absorbing moisture from the air over time. Using the wrong dot brake fluid can lead to the fluid boiling under heavy braking, causing a loss of brake pressure and potentially leading to a brake failure.
Choosing the Right Dot Brake Fluid
To determine the correct dot brake fluid for your vehicle, check your owner's manual or the brake fluid reservoir cap. Most manufacturers recommend using a specific dot-rated fluid, such as DOT 3 or DOT 4. It's important to only use the recommended fluid, as mixing different dot-rated fluids can cause compatibility issues and damage the brake system.
If you're unsure of the correct dot brake fluid for your car, it's best to consult a professional mechanic or the vehicle manufacturer. Using the wrong fluid can lead to expensive repairs and potentially dangerous brake performance.
Does it matter what DOT 4 brake fluid I use?
There are several different types of DOT 4 so be certain you use the correct type. DOT 4 is used in some euro and domestic vehicles. DOT 4 Plus is used in Mercedes and Volvo.
What happens if you use DOT 5.1 instead of DOT 4?
Brake fluids can be mixed only if the fluid that you add to the system belongs to a higher grade. For example, a braking system that has a brake fluid DOT 3 specification can use a DOT 4 or a DOT 5.1 fluid. Also, a system with a DOT 4 can be topped up with a DOT 5.1 without bleeding the system.
Can you mix different DOT brake fluids?
Yes you can mix...the higher the dot number just means it meets higher standards than previous fluids. But do not put in a lower dot number than it requires. If calls for a dot3, you can mix with dot4 or 5. If it calls for a dot5, don't use a dot3.
What happens if I use DOT 5 instead of DOT 4?
They're incompatible, and brake failure may occur if mixed. Moreover, there are serious compatibility issues when using DOT5 in a system that was engineered to use DOT3 or DOT4. Also, users should take care not to mix DOT3 and DOT4 fluids as there could be brake system compatibility issues.
Can I just add brake fluid without flushing?
Yes, you can. You can add brake fluid without removing the old fluid from your reservoir. If your brake system is not exposed to air, then it's okay.
Is all dot brake fluid the same?
Braking fluids DOT 3, DOT 4, and DOT 5.1. are hygroscopic or absorb water and that is why brake fluids have two boiling point values. On the other hand, DOT 5 is a highly hydrophobic silicone formulation, or it repels water, making its boiling points more stable (260 °C dry boiling point and 180 °C wet boiling point).
Can I use DOT 5.1 instead of DOT 3?
It is fully compatible with and can replace or top up systems using DOT 4 and DOT 3 fluids. Since DOT 4 and 5.1 are both glycol-based brake fluids they are compatible with each other, which means they can be readily mixed without harming your brake system.
What happens if I use the wrong brake fluid?
Brake systems use hydraulic fluid that's specially formulated for the purpose. Substituting transmission or power-steering fluid, which are similar to each other, can affect the seals, damage the system, and possibly cause brake failure.
What happens if you use DOT 3 instead of DOT 4?
In these scenarios, using a brake fluid with a low boiling point like DOT 3 could result in the fluid boiling, creating vapors that reduce the hydraulic pressure in the braking system. This causes the brake pedal to feel spongy and unresponsive.
Is DOT 4 or DOT 5.1 better?
DOT 5.1 brake fluid has a higher boiling point of 260°C compared to 230°C DOT4 offers, it will improve the performance of your braking system.
