Hydraulic oil is a non-compressible fluid that plays a vital role in the smooth operation of hydraulic systems. In addition to its primary role in transferring power and heat within hydraulic systems, it has a few secondary functions—contamination removal, sealing, and lubrication.
Hydraulic oil has a wide variety of applications. It powers forklifts and log splitters, allows pilots to control vital systems within aircraft, and ensures the proper functioning of hydraulic brakes on tractors and other farm equipment.
Hydraulic fluids can either be mineral (extracted from naturally occurring crude oil deposits that have undergone a refining process) or synthetic (engineered by chemical synthesis).
The importance of choosing the right hydraulic oil
Using the right type of oil can improve efficiency and reduce wear and tear, which means using less fuel and extending the life of your equipment. There are three essential properties to keep in mind when choosing an oil:
- Multigrade or monograde
- Detergent or no detergent
- Antiwear or no antiwear
Multigrade or monograde hydraulic oil
The grade of an oil describes how temperature affects its viscosity, or thickness. A multigrade oil will maintain viscosity under a greater range of temperatures, so it’s ideal for equipment that has to deal with extreme changes in climate and for starting engines at low temperatures. Monograde oils will suffice for engines that run continuously.
In extreme cold, hydraulic oil is too viscous and this can lead to a considerable drop in efficiency, which can slow machinery down or even cause it to cease functioning. On the other hand, extremely high temperatures can make the fluid too thin, which can make the system less responsive and more susceptible to wear. Multigrade oils have different viscosities at low and high temperatures, and as a result, they are effective throughout the year.
Detergent or no detergent?
Some hydraulic fluids also contain additives known as detergents, which help remove contaminants from hydraulic systems. This can be especially useful for mobile hydraulic applications, such as construction vehicles, where sludge and varnish buildup is common.
Antiwear or no antiwear?
Antiwear additives help reduce damage caused by metal-to-metal contact among hydraulic components such as pistons and valves. That’s an attractive quality for hydraulic systems that operate under very high pressures, such as air compressors.
Avoid mixing different hydraulic oils
Different grades and additives are finely balanced by the manufacturer of any particular oil for a given application, so mixing different fluids in one hydraulic system is typically something to avoid. Mixing fluids with different additives may result in unanticipated and unwanted chemical reactions, which can lead to harmful deposits inside sensitive machinery.