Hydraulic oil and pneumatic (lubricating) oil are two different fluids for entirely different applications. It is important to understand these differences when selecting an oil to use. Choosing the wrong fluid could result in equipment failure or injury.
Hydraulic and Pneumatic
Hydraulic systems use a liquid, such as oil, under pressure to power cylinders, valves, motors and so on. Pneumatic systems use a gas, such as air, under pressure, to power cylinders, valves, motors, among other equipment.
Hydraulic oil, sometimes called hydraulic fluid, is used to transfer energy from one component to another in a hydraulic system. There are several types of oil that may be used in a hydraulic system depending on the individual application. Different oils have varying viscosity and compressibility. The machinery being used typically specifies which type of hydraulic oil is required.
Pneumatic oil, more frequently called lubricating oil, is used to lubricate the moving parts in a pneumatic system. Pneumatic oil typically has a low viscosity and is easily atomized so it can be transported by the compressed air in the system. Some systems will have an oil reservoir that automatically dispenses lubricating pneumatic oil, while others require the operator to manually add a few drops of oil every so often.