How to choose the right hydraulic oil?

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). 

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.  

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.