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This article will cover the differences between power steering and brake fluids.

Understanding the distinctions between different fluids is crucial to the upkeep of our vehicles, as they considerably affect both the performance and safety of our cars.

Although both fluids serve to improve our driving experience, they have distinct purposes and properties that make them vital for their respective systems.

power steering vs brake fluid infographic

Key Takeaways

  • Power steering fluid is specifically designed to help drivers gain better control over the steering wheel by reducing drag on the engine and optimizing the performance of the power steering system.
  •  The braking system relies on brake fluid as a vital element that reduces friction and enables the car to come to a stop.
  •  Brake fluid is incompressible, has a very high boiling point, and contributes to the overall safety and efficiency of the car’s brakes.
  •  While power steering fluid and brake fluid share some similarities, such as having high boiling points, their differences make them incompatible and not interchangeable.
  •  Substituting one fluid for the other could harm the vehicle significantly and jeopardize safety while driving.

What is Power Steering Fluid?

Power steering fluid is a hydraulic fluid formulated explicitly for use in the power steering systems of automobiles. Its primary function is to provide the necessary hydraulic pressure to assist in turning the vehicle’s wheels.

In addition, power steering fluid also serves as a lubricant for the various metal-to-metal components in the system, ensuring smooth operation and reducing wear over time.

Power steering fluid generally has an amber color and can be found in the power steering reservoir of a vehicle’s hydraulic system.

checking power steering fluid level

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Power Steering System Components

The power steering system has several key components that work together to ensure proper steering assistance. The power steering pump, usually situated on one side of the engine and powered by a belt, is among the primary components.

The pump creates the hydraulic pressure needed for the power steering system to function effectively.

Another essential component is the power steering reservoir, which houses the power steering fluid. In some vehicles, the reservoir is mounted on the power steering pump itself, whereas in others, it may be found remotely mounted on the inner fender due to space constraints.

Regardless of location, it is essential to check the fluid levels and ensure they are within the recommended range, as low or high levels can cause problems with the power steering system.

power steering pump on white background

Common Types of Power Steering Fluid

One may come across a few common types of power steering fluid, each with unique properties and applications. Some of the most prevalent types are:

  • Dexron/Mercon: These fluids are often used in power steering systems for various automobile manufacturers. They are petroleum-based and can also be found in automatic transmission systems. These fluids are compatible with multiple vehicles, including those from manufacturers such as Volvo and BMW.
  •  Automatic Transmission Fluid (ATF): In some cases, ATF can be utilized as a power steering fluid, providing an alternative for certain vehicles. However, referring to the vehicle’s owner’s manual is essential to ensure ATF usage is appropriate for the specific make and model.
  •  Mineral Oil: Mineral oil-based power steering fluids are less common but still used in particular applications. These fluids may be found in older vehicles or those with specific requirements by the manufacturer.
  •  Synthetic Power Steering Fluid: Synthetic power steering fluids offer enhanced performance over their petroleum-based counterparts, including improved low viscosity and longer service life. These fluids are commonly employed in high-performance or luxury vehicles.
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The owner’s manual indicates that using the appropriate power steering fluid for your vehicle is essential. Using an incorrect fluid can result in harm to the power steering system, and it may result in inadequate performance or expensive repairs.

What is Brake Fluid?

Brake fluid is a type of hydraulic fluid used in vehicles’ braking systems. It is responsible for transmitting force and pressure from the brake pedal to the brake components, such as the calipers and wheel cylinders, which then apply the brakes to stop the vehicle. 

Brake fluid is designed to endure high temperatures and pressure, and it is essential to use the correct type of brake fluid as specified by the vehicle manufacturer to ensure the safe and efficient operation of the braking system.

This fluid must have a high boiling point and be incompressible to ensure that it can maintain the proper force when braking. Because a vehicle’s braking system generates significant heat, the brake fluid must resist boiling at high temperatures to avoid brake failure.

Furthermore, because brake fluid is hygroscopic, it absorbs moisture to maintain a low freezing point and prevent corrosion in the brake lines.

Brake fluid reservoir and brake booster of the car

Braking System Components

Understanding the braking system components will help you appreciate the importance of brake fluid. The main components include the brake pedal, master cylinder, brake lines, calipers, wheel cylinders, and brake pads or shoes.

When you apply pressure to the brake pedal, the master cylinder forces the brake fluid through the brake lines to the calipers or wheel cylinders.

This pressure causes the brake pads or shoes to clamp onto the brake discs or drums, creating friction and slowing down or stopping the vehicle.

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The brake fluid must be able to maintain its properties under varying temperatures and environmental conditions to ensure the efficiency and safety of the braking system.

Common Types of Brake Fluid

There are several common types of brake fluid, which are differentiated by their Department of Transportation (DOT) ratings. The most popular types are DOT 3, DOT 4, DOT 5, and DOT 5.1, each with distinct specifications and boiling points.

  • DOT 3: Glycol-ether based and widely used in many vehicles. It has a lower dry and wet boiling point than higher DOT-rated fluids, making it more susceptible to moisture absorption.
  •  DOT 4: Also glycol-ether based, but formulated for higher performance vehicles. It has a higher boiling point than DOT 3 and offers better heat resistance, making it suitable for more demanding brake systems.
  •  DOT 5: Silicone-based and not hygroscopic, meaning it doesn’t absorb moisture. It has a higher boiling point but is not compatible with ABS systems and can lead to potential brake system damage if mixed with other fluid types.
  •  DOT 5.1: Glycol-based, this brake fluid is compatible with ABS systems and has a higher boiling point than DOT 3 and DOT 4. It’s primarily used in high-performance vehicles and racing applications.

Using the appropriate brake fluid is essential to maintain the functionality and longevity of a vehicle’s braking system.

Brake Fluid with Disk Brake, 3D rendering isolated on white background

Differences Between Power Steering Fluid and Brake Fluid

Physical and Chemical Properties

Power steering fluid and brake fluid have different base components in their formulations. Power steering fluid is mineral oil-based or synthetic, while brake fluid is usually glycol-based or silicone-based.

This means they have distinct characteristics regarding properties such as viscosity, lubrication, and ability to withstand pressure and temperature changes.

Functions and Mechanisms of Action

Power steering fluid serves as a hydraulic fluid in the power steering system of a vehicle, making it easier to turn the steering wheel.

This fluid undergoes pressure changes within the steering gear, enabling responsive control over the steering mechanisms. On the other hand, brake fluid operates within the hydraulic braking system by creating a high-pressure force, allowing the vehicle to stop when the brake pedal is pressed.

Brake fluid transfers the force applied on the brake pedal to the brake pads, which generates friction to halt the vehicle.

Compatibility and Interchangeability

Due to their distinct properties and functions, power steering fluid and brake fluid are not interchangeable. Using the wrong fluid may damage the respective systems, cause corrosion or moisture problems, and significantly impair the safety and performance of the vehicle.

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