Difference Between Hydraulic Fluid and Hydraulic Oil

The key difference between hydraulic fluid and hydraulic oil is that hydraulic fluid is used in automatic transmissions in automobile systems whereas hydraulic oil can not be used for this purpose.

Hydraulic oil is the most common form of hydraulic fluids. Therefore, many people tend to use these two terms interchangeably.

1. Overview and Key Difference
2. What is Hydraulic Fluid
3. What is Hydraulic Oil
4. Side by Side Comparison – Hydraulic Fluid vs Hydraulic Oil in Tabular Form
5. Summary

What is Hydraulic Fluid?

Hydraulic fluid is the medium that is useful in energy transferring in hydraulic systems such as excavators, backhoes, hydraulic brakes and garbage trucks. Although the primary use of hydraulic fluids is to transfer energy, there are some secondary uses as well. Ex: heat transfer, removal of contamination, sealing, lubrication, etc. The most important characteristics of hydraulic fluid are as follows:

Thermal stability
Hydrolytic stability
Low chemical corrosiveness
Low tendency to cavitate
Long life
Low cost, etc.

Difference Between Hydraulic Fluid and Hydraulic Oil

Figure 01: Hydraulic Brake Fluid

When choosing a hydraulic fluid, we should consider the viscosity of the fluid. The fluid should have a minimum viscosity at the highest operating temperature. In addition, foaming of hydraulic fluid is a problem that arises when using a hydraulic fluid. Foam can degrade and affect the performance of the system. Therefore, we should remove the foam that produces in the fluid.

What is Hydraulic Oil?

Hydraulic oil is a flammable fluid that is useful in energy transfer in a hydraulic system. However, since it is flammable, it is not a good option to use this fluid in an igneous source. That is because, under high-pressure conditions, the oil spray can ignite. Due to this reason, people made hydraulic fluid to use in the place of hydraulic oil as a solution to this flammability.

Hydraulic oil consists of oil and additives. This oil acts as a medium for energy transfer as well as a lubricant and coolant. This oil can reduce the corrosion in hydraulic systems, and it can perform under a wide range of temperatures. There are three common forms of hydraulic oils;

General hydraulic oil – this oil is useful in general hydraulic machinery due to its antifriction properties and oxidation stability.
Wear-resistant hydraulic oil – this oil is useful in special machinery that operates under high-pressure conditions and high temperatures.
Flame retardant hydraulic oil – this oil is useful in machinery with a risk of ignition or fire.

What is the Difference Between Hydraulic Fluid and Hydraulic Oil?

Hydraulic Fluid vs Hydraulic Oil
Hydraulic fluid is the medium that is useful in energy transferring in hydraulic systems such as excavators, backhoes, hydraulic brakes and garbage trucks.	Hydraulic oil is a flammable fluid that is useful in energy transfer in a hydraulic system.
Flammability
Has less or no flammability	Highly flammable
Operating Conditions
This can perform at a wide range of temperatures and pressures.	This ignite or fire under high pressure and temperature conditions.
Uses
Has many applications such as in automatic transmissions in automobile systems, power brakes and steering.	Is important as a medium for energy transmission, as a coolant and lubricant.

Summary – Hydraulic Fluid vs Hydraulic Oil

Hydraulic oil is a form of hydraulic fluid. Hydraulic fluid reduces the harmful effects of hydraulic oil such as flammability at high-pressure conditions. The difference between hydraulic fluid and hydraulic oil is that hydraulic fluid is useful in automatic transmissions in automobile systems whereas hydraulic oil cannot be used for this purpose.

Reference:

1. 01, Jan. “Engineering Essentials: Hydraulic Fluids.” Hydraulics & Pneumatics, 14 Mar. 2017. Available here
2. “Types of Hydraulic Oil｜Technical Information｜Apiste Corporation.” Apiste. Available here