Hydraulic systems are used in nearly all areas of automotive production, including press shops, machine shops and general assembly. The drive for lower costs and improved productivity has led to significant changes in hydraulic component technology, resulting in more compact and more powerful equipment. For example, modern hydraulic systems feature reservoirs 60 to 80% smaller than those of older systems, yet the same equipment must operate over increasing system pressures.

Even small amounts of contamination or fluid degradation can damage hydraulic components, especially servo and proportional valves. This is further complicated through these smaller, power-dense systems having a limited residence time in which to reject contaminants such as solid particles or air, while still operating at higher temperatures that can both stress internal fluids and system components.

How can plant managers and equipment maintenance professionals ensure that they properly protect their company’s investment in a modern hydraulic system?

There are two important routes to enhancing the performance and durability of a hydraulic system; by using high-performance hydraulic fluids and devising and implementing a proactive maintenance and oil analysis plan.

By following the tips below, plant managers, equipment maintenance professionals or purchasing agents can make informed decisions when it comes to selecting the right hydraulic oil and developing the right hydraulic system maintenance plan to help ensure their operations remain competitive and productive.

What to look for in a hydraulic fluid

Right specifications – One starting point for selecting a hydraulic lubricant is the original equipment manufacturer’s (OEM’s) recommendation. This may be specific to the machine manufacturer or the hydraulic component manufacturer. The OEM’s recommendation typically provides the appropriate viscosity grade for the expected operating temperature and pressure range. It also indicates a minimum level of specifications and performance level, such as having Denison HF-0, Eaton/Vickers M-2952-S, ISO11158 type HV, DIN51524-HLP (2006, part2).

Right viscosity – Above all, viscosity is the most critical factor when selecting a hydraulic fluid. It is important to match the appropriate viscosity grade to operating temperatures and load conditions that a hydraulic system may undergo on a daily basis. Without the correct viscosity, the system will not operate as designed and the system will likely never reach peak efficiency.

By factoring in the operating conditions of the hydraulic system, it is equally important to realize that OEM-suggested guidelines may not always provide detailed recommendations if the system is subjected to extreme working conditions, such as high or low ambient temperatures. Also, for equipment that is being used outside and subjected to both hot and cold extremes, a highviscosity, multigrade lubricant that features a balanced formulation may be required. In such cases, field application advice from the lubricant supplier can be valuable in helping to make the right choice.

Right performance attributes – Given the higher pressures, higher temperatures and smaller size of modern hydraulic systems, hydraulic fluids must do more than simply satisfy the correct viscosity and OEM specification.

High temperatures and pressures demand fluids that are oxidatively and thermally stable while preventing deposit formation and providing a high degree of anti-wear protection under extreme conditions. The fluid must also possess excellent air release properties, filterability and seal compatibility. Moreover, the very latest generation of hydraulic fluids can also help increase overall hydraulic system efficiency.

A good option is the new Mobil DTE 10 Excel Series, the latest addition to the popular Mobil DTE family of hydraulic oils from ExxonMobil. Designed to handle the lubrication requirements of both industrial and mobile high pressure hydraulic systems, the Mobil DTE 10 Excel series features a revolutionary formulation that delivers exceptional oil life while maintaining hydraulic system cleanliness, enhanced system efficiency and component protection in modern hydraulic systems.

The Mobil DTE 10 Excel Series lubricants help keep hydraulic systems running cleaner, extending machine reliability and helping increase productivity through improved machine availability. Proprietary Mobil Hydraulic Fluid Durability (MHFD) testing has demonstrated that Mobil DTE 10 Excel Series’ ultra keep-clean properties demonstrate a significant improvement in cleanliness versus the competitive products evaluated.

The product’s high viscosity index and outstanding shear stability enable hydraulic efficiency benefits and hydraulic pump protection over a wide range of operating temperatures. As a result, Mobil DTE 10 Excel Series lubricants help provide plant managers and equipment maintenance professionals with maximum equipment protection at high- and low-temperature extremes, offering the valuable option of using one hydraulic fluid brand across many applications, in turn helping to simplify inventory management.

Hydraulic efficiency benefits can translate to increased machine productivity and/or reduced fuel consumption.

In controlled laboratory testing, the Mobil DTE 10 Excel series demonstrated up to 6% increase in hydraulic pump efficiency. In controlled field testing, up to a 6% reduction in fuel consumption (results dependant on operating conditions) per work cycle was documented in hydraulically driven excavators.

Best practices for hydraulic system maintenance

Keep it clean – Keeping hydraulic systems clean is a must for all environments. The combination of high pressures, small reservoir size and tight tolerance control systems make the exclusion of contaminants crucial in all critical systems.

To keep the system free of contamination, a good place to start is by storing and handling oil properly. Hydraulic lubricants should be stored in a closed container in a controlled temperature environment with adequate spill containment. Transferring hydraulic lubricants should be done through the use of a trolley and dedicated, sealed clean oil dispensing equipment.

Finally, the hydraulic system reservoir should have a high quality desiccant breather and system filter, as recommended in the manufacturer’s guidelines. Some systems utilize auxiliary filtration systems, sometimes known as a kidney loop, that continually ‘polish’ the hydraulic fluid to maintain system cleanliness.

Oil analysis – As part of routine maintenance, the ‘health’ of the hydraulic oil and the hydraulic system itself should be regularly checked.

Typically, it is advised that maintenance professionals perform quarterly oil analyses and annual system inspections. For systems critical to a plant’s operation or for those subjected to challenging conditions, more frequent oil analysis should be considered.

The oil analysis should include a measurement of fluid viscosity, water content, particle count and dissolved metals to determine how well the system is operating. Examining changes in the oil analysis data over time, also known as ‘trending’, is necessary to assess the condition of the hydraulic fluid. By trending oil analysis data it is possible to proactively address undesirable conditions before they become problems.

For plant managers and equipment maintenance professionals who want an effective oil analysis program that can also save time and money, there is Exxon Mobil’s proprietary online Signum oil analysis program.

Signum oil analysis offers engineers immediate access and direct control of their lubricant sampling programme. With a few keystrokes, users can manage their oil analysis needs with the following services:

  • Update equipment registrations and select analysis options based on their equipment or maintenance needs
  • Track the status of samples at the lab
  • Direct actions based on analysis results, request sample kits
  • Share critical results with colleagues in a secure, password protected environment.

Visual inspections – Beyond oil analysis, visual system inspections should be conducted regularly to check and document the condition of the hydraulic systems. Inspection data can be used to establish the optimum time to perform maintenance on critical hydraulic components such as filters, breathers, valves, hoses, heat exchangers and pumps.

Comprehensive leak detection should also be performed, especially if excessive hydraulic oil usage is noted during a routine system inspection.


Today’s hydraulic units are far more sophisticated than ever before. Even more so than their predecessors, these new, compact, high-pressure hydraulic systems must be protected with fundamental best practices – such as using a high performance hydraulic lubricant and implementing a proactive oil analysis programme.