Difference Between Power Steering Fluid and Brake Fluid

Table of Contents

Power steering fluid and brake fluid are both vital to the safety and performance of a vehicle, yet they serve distinct roles within the automotive system. Understanding the differences between these two fluids can help ensure they are used correctly, maintaining the vehicle's integrity and safety.

Direct Comparison

Feature Power Steering Fluid Brake Fluid
Primary Function Facilitates steering of the vehicle Transfers force from the brake pedal to the brake pads
Composition Mineral or synthetic oil-based Glycol-ether, silicone, or mineral oil-based
Hydraulic System Power steering system Brake system
Boiling Point Varies, generally lower than brake fluid High boiling point to prevent vapor lock
Viscosity Varies, designed for hydraulic pump Typically less viscous than power steering fluid
Compatibility Specific to vehicle make and model DOT ratings ensure broader compatibility
Replacement Interval Typically longer than brake fluid Recommended every 1-2 years
Safety Risks Minimal direct safety risk Essential for braking system's effectiveness

Detailed Analysis

Primary Function

The power steering fluid is designed to transmit power in the steering system, making it easier for the driver to turn the steering wheel. In contrast, brake fluid operates within the brake lines, transferring the force applied by the driver on the brake pedal to the brake pads, which then slow down or stop the vehicle.


Power steering fluids can be mineral oil-based or synthetic, tailored to the specific requirements of the vehicle's steering system. Brake fluids are classified into glycol-ether based (most common), silicone-based (DOT 5), and mineral oil-based (used in certain systems), each with distinct properties and applications.

Hydraulic System

Each fluid operates in a different hydraulic system within the vehicle. Power steering fluid is used within the power steering system, which includes the pump, rack, and pinion. Brake fluid is used within the brake system, which encompasses the master cylinder, brake lines, and calipers.

Boiling Point

Brake fluid is formulated to have a high boiling point to prevent vapor lock and maintain its effectiveness under high temperatures generated during braking. Power steering fluid, while also resistant to heat, typically has a lower boiling point than brake fluid because the steering system does not generate as much heat.


The viscosity of power steering fluid is formulated to ensure optimal performance of the power steering pump and rack. Brake fluid viscosity is generally lower, tailored to its need to flow quickly and efficiently through the brake lines, even in cold temperatures.


Power steering fluid requirements can vary significantly between vehicle makes and models, necessitating specific formulations. Brake fluids are standardized with DOT (Department of Transportation) ratings (e.g., DOT 3, DOT 4, DOT 5) to ensure compatibility across a wide range of brake systems.

Replacement Interval

Brake fluid absorbs moisture over time, which can lower its boiling point and lead to system corrosion. Therefore, it is recommended to replace brake fluid every 1-2 years. Power steering fluid typically has a longer service life but should be replaced as per the manufacturer's recommendation or if the system shows signs of contamination or degradation.


Understanding the distinctions between power steering fluid and brake fluid is crucial for proper vehicle maintenance and safety. While both are hydraulic fluids, their composition, function, and the systems they operate within differ significantly. Using the correct fluid according to the vehicle manufacturer's specifications is essential to ensure the longevity and reliability of your vehicle.


Q: Can I use brake fluid in my power steering system?
A: No, using brake fluid in your power steering system can cause damage to the system's components due to differences in composition and properties.

Q: How often should I check my power steering and brake fluid levels?
A: It is advisable to check both fluid levels regularly, such as during routine maintenance or oil changes, to ensure they are within the recommended range.

Q: What happens if I use the wrong type of brake fluid?
A: Using the wrong type of brake fluid can lead to reduced braking performance, damage to the brake system components, and ultimately, a failure of the braking system.

Q: Can mixing different types of brake fluid cause problems?
A: Yes, mixing different types of brake fluid (especially mixing glycol-ether based fluids with silicone-based DOT 5) can lead to reduced effectiveness, damage to the system, and safety hazards. Always follow the vehicle manufacturer's recommendations.