Today’s environmentally aware hydraulic fluids, both vegetable oil and synthetic products, can easily meet or exceed most industry standards, such as:

• Vickers M-2950-S,

• Vickers 1-286-5,

• Vickers 35VQ-25 and V-104C (ASTM D-2882) vane pump stand tests,

• Vickers M-2950-S, I-286-S,

• U. S. Steel 126 and U.S. Steel 127,

• Cincinnati Milacron P-68, P-70,

• DIN 51524 Part 2 load stage 10, and

• Denison HF-0, HF-1, HF-2.

Primary applications

Environmentally acceptable hydraulic fluids are typically used in situations where an oil spill would be small, but difficult to prevent, such as older mobile hydraulic systems. Other instances would be where a spill may be rare, but would pose a serious environmental or public relations problem (e.g., an offshore oil platform or hydraulic systems on equipment operating in urban or residential areas).

Primary markets for hydraulic EAFs include forestry, mining, marine and offshore, hydroelectric dams, and mobile hydraulic systems that operate in urban or residential areas. Synthetic esters should be considered in applications that run at high or low temperatures, for OEM original fill, or for hydraulic applications that require longer service life. Such applications take advantage of the synthetic ester’s unique characteristics, thus justifying their higher cost.

Vegetable oils best serve hydraulic-fluid applications that operate in normal temperature ranges, or in “use and lose” applications where the oil is lost immediately to the environment (drill oils, bar and chain oils, cable lubes, etc.). Vegetable-based oils are the least expensive of the four different EAF types, and today’s fluids are stable and do an excellent job of protecting equipment.

Comparing the fluids

The characteristics of the HETG natural ester often surpass those of the HEES synthetic ester (Table 2). At high temperatures, though, the synthetic fluid offers far better oxidation stability and, therefore, service life.  And at very-low temperatures, the synthetic ester flows freely, while the vegetable oil product solidifies at about −30°F.

Hydraulic fluid spills come in various forms. They can occur over time, with a drop-by-drop loss of a quart of oil per week. On the other hand, it might be an immediate, rapid spill, such as a hydraulic hose bursting on an oil platform or the release of oil on heavy equipment that continues until a pump can be turned off.

In the U. S., spills of EAFs must be reported to the National Response Center, U. S. Coast Guard, and local authorities —  just as for spills of mineral oils. Generally, EAFs are less toxic and faster to biodegrade than spills of mineral oil lubricants.  Cleanup and remediation requirements and costs are normally lower for spills of EAFs than for spills involving mineral oils.

Environmental laws have driven these changes, and in some cases push new, more-restrictive laws. For example, North Sea drilling platforms require that a hydraulic fluid must meet certain environmental standards, which vary depending on the quantity used and the location. Every passing year seemingly brings more hydraulic and pneumatic oil applications under tighter environmental restrictions.


Regulations propel the development and application of enhanced environmentally acceptable fluids. Thanks to new base oils and additives, the latest-generation products are able to meet performance standards that were once only relegated to mineral oils. Equipment owners now can protect both their hydraulic equipment as well as the environment by choosing the right product for their application.

David Sundin, Ph.D., is a chemist, engineer, and founder of SVB Environmental Lubricants, Tyler, Tex. He can be reached at (903) 231-3141 or visit his Web site at