Hydraulic Fluid vs. Hydraulic Oil: Understanding the Differences

June 18, 2024

Hydraulic systems are integral to a wide array of machinery and equipment, powering everything from industrial machines to automotive brakes. A crucial component of these systems is the hydraulic medium—typically either hydraulic fluid or hydraulic oil. While these terms are often used interchangeably, there are distinct differences between the two that can impact the performance, longevity, and maintenance of hydraulic systems. In this blog, we will explore these differences, helping you make informed decisions for your hydraulic applications. Lets understand the differences between hydraulic fluid vs. hydraulic oil.

What is Hydraulic Fluid?

Hydraulic fluid is a broad term that encompasses any liquid used within a hydraulic system to transmit power. This can include various types of oils, but it also covers other fluids such as water-based solutions and synthetic alternatives. Hydraulic fluids are specifically designed to provide the necessary flow characteristics and pressure transmission properties required for hydraulic systems.

Types of Hydraulic Fluids:

  1. Petroleum-Based Fluids: Traditional hydraulic oils derived from refined crude oil.
  2. Water-Based Fluids: Including water-glycol solutions and water-oil emulsions, used where fire resistance is crucial.
  3. Synthetic Fluids: Man-made chemicals designed to offer superior performance under extreme conditions, including esters and silicones.

What is Hydraulic Oil?

Hydraulic oil is a subtype of hydraulic fluid, specifically referring to petroleum-based oils. It is the most commonly used hydraulic fluid due to its excellent lubricating properties, thermal stability, and cost-effectiveness. Hydraulic oils are formulated to meet the demands of high-pressure systems and provide protection against wear, corrosion, and oxidation.

Properties of Hydraulic Oil:

  1. Viscosity: Hydraulic oils are engineered to maintain optimal viscosity across a range of operating temperatures.
  2. Lubricity: High lubricating properties reduce friction and wear in hydraulic components.
  3. Thermal Stability: Resistance to thermal degradation ensures performance consistency under varying temperatures.
  4. Oxidation Resistance: Additives in hydraulic oil prevent oxidation, extending the fluid’s service life.

Key Differences Between Hydraulic Fluid vs. Hydraulic Oil

  1. Composition:
    • Hydraulic Fluid: Can be petroleum-based, water-based, or synthetic.
    • Hydraulic Oil: Specifically petroleum-based.
  2. Applications:
    • Hydraulic Fluid: Versatile, used in environments requiring fire resistance, biodegradability, or where extreme temperatures are present.
    • Hydraulic Oil: Predominantly used in industrial machinery, automotive, and heavy equipment due to its robustness and cost-effectiveness.
  3. Performance:
    • Hydraulic Fluid: Can be tailored for specific conditions, offering specialized performance such as fire resistance or low-temperature fluidity.
    • Hydraulic Oil: Generally offers superior lubrication and protection against wear and tear in high-pressure systems.
  4. Environmental Impact:
    • Hydraulic Fluid: Options like biodegradable fluids minimize environmental impact in case of leaks or spills.
    • Hydraulic Oil: Typically non-biodegradable, with potential environmental hazards if not managed properly.

Choosing the Right Hydraulic Medium

Selecting between hydraulic fluid and hydraulic oil depends on the specific needs of your hydraulic system and the operating environment. Here are some factors to consider:
  1. Operating Conditions: High temperatures, potential fire hazards, or extreme pressures might necessitate a specialized hydraulic fluid.
  2. Environmental Concerns: Biodegradable hydraulic fluids are preferable in environmentally sensitive applications.
  3. System Requirements: Check manufacturer recommendations for the best-suited fluid type for your equipment.
  4. Cost and Availability: While hydraulic oils are generally more cost-effective, specialized fluids might offer long-term savings through enhanced system protection and longevity.


Understanding the differences between hydraulic fluid vs. hydraulic oil is essential for maintaining the efficiency and longevity of hydraulic systems. While hydraulic oils are the most common choice due to their excellent performance and cost-effectiveness, specialized hydraulic fluids offer unique benefits for specific applications. Always consider the operating conditions, environmental impact, and manufacturer recommendations when choosing the right hydraulic medium for your needs. By making an informed decision, you can ensure optimal performance and reliability of your hydraulic systems. Contact us to know about more information about hydraulic fluid vs. hydraulic oil.

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