23.9 kW * 0.048 * 1,000 hrs

= 1,147.2 kWh * 0.0573 gal of diesel fuel/kWh

= 79.3 gal of fuel saved


24.2 kW * 0.201 * 1,000 hrs

= 4,864.2 kWh * 0.0691 gal of diesel fuel/kWh

= 336.3 gal of fuel saved

Total: = 79.3 + 336.3

= 415.6 gal of fuel saved

Assuming a diesel fuel cost of $1.72/gallon, the cost savings would be:

415.6 gal * $1.72/gal = $715 per pump

With a fleet of 100 vehicles (total of 200 pumps) the total cost savings to perform the same amount of work would be: $715 per pump * 200 pumps = $143,000 annually.

When considering environmental impact, a fleet of 100 vehicles would conserve 83,123 gal of fuel, corresponding to a reduction of approximately 817 tons of CO2 emissions.

The result shows that by selecting the proper multigrade hydraulic fluid, an operator can significantly reduce fuel use in hydraulic pump operations for a given amount of work, thereby reducing operating costs. For the owner of a medium-sized fleet, this can translate into an annual savings of approximately $143,000. For larger fleet operations, the savings are significantly greater.

In preparing to change from monograde hydraulic fluids to a single multigrade fluid, the key factors to examine are maximum operating pressure, minimum and maximum operating temperatures, and the viscosity recommendations provided by the pump manufacturer. This will likely include the maximum startup viscosity under load, the range of optimum operating viscosity, and the minimum and maximum operating viscosity.

The relative performance of available multigrade fluids should be compared before one is selected. All multigrade fluids are not created equal. A VHVI multigrade hydraulic fluid such as Hydrex XV will not only provide good energy efficiency, it also has additional performance benefits.

Hydrex XV is a very high viscosity index, high performance, long-life, anti-wear hydraulic fluid, designed for all season use in heavy-duty hydraulic systems. By removing impurities that can hinder the performance of conventional oils, and blending in specialty additives, it is said to last longer than competitive fluids. It allows hydraulic systems to start at temperatures as low as -40° F, under no-load conditions.

In today's operating environment, where maximizing equipment productivity is essential, switching to a multigrade hydraulic fluid is a significant step to reducing costs. Fuel consumption for a given amount of work may be significantly reduced, seasonal oil changes eliminated and maintenance time decreased. At the same time greenhouse emissions can be lowered. Switching to a VHVI premium multigrade fluid can improve equipment protection even further, resulting in even greater cost savings and equipment protection.

Brenda Jones is a hydraulics engineer with Petro-Canada Lubricants, Calgary, Alta. She acknowledges RohMax USA, Inc., for research information and consultation.