The main difference between a hydraulic fluid and a hydraulic oil is down to usage. A hydraulic fluid is employed in the automatic transmissions of automobile systems, but hydraulic oils cannot be utilised for this purpose.
However, hydraulic oil is recognised as the most common form of available hydraulic fluid, leading many people to use these two terms interchangeably, even though they are not the same thing.
What exactly is hydraulic fluid?
Essentially, hydraulic fluid is a medium used to transfer energy transferring within hydraulic systems, like the kind used in hydraulic brakes and by excavators and rubbish collection trucks. While the main use of a hydraulic fluid is to transfer energy, these solutions have multiple benefits, including sealing, lubricating and removing contaminants.
When selecting a hydraulic fluid, companies must consider viscosity. The hydraulic fluid should always offer a minimum viscosity for the highest temperature required during operation. Foaming can be an issue in hydraulic fluid as foam produced can degrade and impact the performance of a hydraulic system. As a result, any foam produced in the fluid should be removed.
How do you define hydraulic oil?
A flammable fluid, hydraulic oil is used for energy transfer within hydraulic systems. Since this lubricant is flammable, it is never a suitable option when a fluid is required where ignition could occur, as under high-pressure conditions any hydraulic oil spray can potentially ignite. For this reason, hydraulic fluid was developed to use as an alternative to hydraulic oil, solving the flammability issue.
Hydraulic oil is manufactured with a base oil and selected additives. It provides an energy transfer medium while cooling and lubricating systems. It can effectively reduce corrosion in hydraulic systems and can perform efficiently under an extensive range of operating temperatures.
What are the most common types of hydraulic oil?
The three most common hydraulic oils are as follows:
• General hydraulic oil has excellent oxidation stability and antifriction properties, making it ideal for general-purpose hydraulic machinery
• Wear-resistant hydraulic oil is designed for machinery operating under high-pressure and at high temperatures
• Flame retardant hydraulic oil is used in machinery where there is potential risk of fire or ignition
The key differences between hydraulic fluid and hydraulic oil
The terms hydraulic fluid and hydraulic oil are often misused. While a hydraulic oil is a hydraulic fluid, a hydraulic fluid doesn’t always include oil.
The simplest way of understanding the difference between these products is to consider hydraulic fluid as a broader range of hydraulic solutions, of which hydraulic oil is just one specific type.
The oldest and most affordable hydraulic fluid is water, which historians state was used in Ancient Egypt to irrigate crops and later tell the time. However, hydraulic fluids can also be salt solutions, water-oil emulsions and hydraulic oil.
In formulation, a hydraulic oil is a petroleum-based product, while the name hydraulic fluid encompasses solutions that include a mix of ingredients like water, mineral oil and synthetic compounds.
Hydraulic fluids are defined as an energy transfer medium within hydraulic systems. Hydraulic oils are flammable and highly explosive, while hydraulic fluids that contain little to no oil have low to non-existent flammability.
As a result, a hydraulic oil will catch fire if exposed to high pressures and temperatures, while a low to no oil fluid can work at various pressures and temperatures in normal operating conditions.
Types and uses of hydraulic fluid
Hydraulic fluids, manufactured by brands like Mobile and Fuchs, fit into one of three key categories: water-based, petroleum-based and synthetic-based.
Fluids that are based on water
Today, hydraulic fluids with a water-base are the least common. While critically required for high fire ignition risk area, they provide low levels of lubrication for hydraulic systems.
Petroleum-based fluids
These can provide superior stability, corrosion resistance and lubrication for pumps and other hydraulic system components.
Fluids made from synthetic materials
Synthetic hydraulic fluids are formulated to offer next-level lubrication, fluid stability and other benefits. For example, they can seal systems and their components, dissipate heat, help prevent system corrosion and inhibit the build-up of contaminants. They can work at high pressures and a wider temperature range pressure than other types of hydraulic fluids; however, they are often more expensive to use than oil and water-based fluids. Additionally, they are not always compatible with standard sealants, so always check before purchasing.
In summary, hydraulic oil is a type of hydraulic fluid. However, unlike hydraulic oils, hydraulic fluids are used in automatic transmissions and are an alternative to hydraulic oil when flammability is a potential issue involved in operating environments.
