Many hydraulic systems can operate with a wide range of oils, but does it matter which one you choose?
Hydraulic systems are found in a multitude of applications and operating conditions, so it’s impossible to point to a single solution, but here are some factors to consider.
Viscosity grade
When picking a hydraulic oil, it’s vital to have the right viscosity grade for your application, because if you get this wrong, the components in the hydraulic system will degrade more rapidly than they should.
The basis for working this out is the optimum and permissible viscosity range for the hydraulic components, but operating temperatures also affect viscosity, so you also need to consider the viscosity at start-up conditions and at the maximum expected operating temperature.
Mineral versus synthetic hydraulic oil
Products based on synthetic technology often come at a price premium, but they can also deliver tangible benefits that can more than compensate for the high purchasing cost.
For example, Mobil claims that its Mobil DTE 10 Excel series can improve hydraulic pump efficiency by up to 6%, while lasting up to three times longer when compared to Mobil’s conventional hydraulic fluids.
Should you use a multigrade oil?
Hydraulic systems can sometimes need to function in a wide range of operating conditions, from sub-zero temperatures in winter to warm conditions in summer.
Keeping the viscosity within an acceptable range will likely need a multigrade hydraulic oil in such cases.
Nevertheless, multigrade oils can have disadvantages, so if your system operates in a narrow temperature range, such that optimal viscosity can be maintained with a monograde oil, it’s generally preferable to opt for that over multigrade oil.
What about detergent oils?
Some hydraulic oils contain detergents and dispersants to break up and suspend contaminants, like sludge and varnish, and emulsify water. This may not necessary be ideal in industrial systems, where contaminants have the opportunity to precipitate and settle in a relatively large reservoir, but it can be desirable for mobile systems with smaller reservoirs.
Other factors
You may also want to consider whether you’ll need a zinc-free solution to prevent hydrolysis or corrosion problems or address environmental concerns. You’ll also want to make sure that a hydraulic oil is compatible with the rubber and elastomer components in a system, such as seals and gaskets.
