Hydraulic Oils

All hydraulic oils are the same aren’t they?

While hydraulic oil standards are commonly agreed to and well established, the relative performance of hydraulic oil varies. This is due to variations in approaches and experience in formulating products, variations in the base oils used (hydraulic oils are in excess of 98 percent base oil) and different target applications and performance. Additionally, there are hydraulic oils that emulsify water, and those that demulsify water. Demulsifying and emulsifying hydraulic oils are typically not compatible due to the nature of their chemistries. For the purpose of this FAQ, we are addressing demulsifying hydraulic oils.

What are the key differences in hydraulic oils?

Variations in the base oil and performance additives used are the primary differences in hydraulic oils. To manage costs, some lubricants manufacturers use a variety of base oils and additives. This can lead to performance differences in these areas: oxidation, water handling ability, sludge formation, filter life, productivity, fuel efficiency, anti-wear/extreme pressure (EP), cold temperature pumpability. Consistent performance standards are important to help ensure risk-free equipment operation, and higher quality hydraulic oils meet or exceed these standards. The use of different types of performance additives in the formulation can make a big difference. The approaches can vary, including the use of more or less zinc (an element in a key anti-wear additive), or the use of no zinc at all, such as in ashless hydraulic oils.

What do Original Equipment Manufacturers (OEMs) say about higher quality hydraulic oils?

OEMs are very specific about the quality of lubricant used in their equipment and for very good reason. If the lubricant fails, so does their equipment. It is important to follow OEM guidance for warranty and for the extended life of your equipment. Off-highway emission standards are becoming stricter—leading to a need to improve fuel efficiency. In mobile equipment such as excavators, fuel economy is linked to engine performance and hydraulic system efficiencies. By improving hydraulic system efficiencies, equipment can use less fuel per hour and increase production per hour—leading to improved utilization. Hydraulic system pressures are also increasing, thus resulting in higher operating temperatures, which causes increased demands on the hydraulic fluids. In combination with these systems-related demands, equipment builders are moving to extended service intervals for fluids. Due to higher hydraulic system pressures and the need for extended service life, OEM recommendations are moving to higher performance products.

What does FZG mean in relation to hydraulic oils?

FZG is a test normally reserved for gear oils to measure gear performance. It is a test reflective of combined EP/ AW performance in gear sets. Some compa- nies include the FZG result in published data. Some hydraulic oil products with gear performance can indeed be used in lightly loaded gearboxes, but often their use is limited to smaller high-speed gearboxes because of the lower viscosities used in hydraulic oils. FZG results are given on a scale of 1-12 with 12 being the highest performance. For example, Clarity® Hydraulic Oil AW 32, 46, 68 has an FZG rating of ≥ 12, whereas, Rando HDZ 32 has a rating of ≥ 11, and Rando HDZ 46, 68, 100 have a rating of ≥ 12.

SOURCE | SHUTTERSTOCK / EZIU

Are there any advantages to ashless formulations for hydraulic oils?

Properly formulated ashless formulations have a high FZG rating making them suitable for light gear service. Also, the technology employs base oils with a higher viscosity index. This improves low-temperature start performance and better film thickness at elevated temperatures. This can provide an opportunity to rationalize the number of products in use at a certain location while improving pump efficiency. .

This article is courtesy of Chevron lubricants. Clarity® Hydraulic Oil AW and Rando HDZ are some of the hydraulic oils they have.