Except for specialized applications like mining or aircraft, most products were seen as cheap and interchangeable. Users selected their hydraulic fluid by viscosity grade – lighter in the winter, a little heavier in the summer – and price. And if a piece of equipment leaked in the field (they always leaked), a dollop of automatic transmission fluid or even motor oil would do in a pinch.

Today, mobile hydraulic equipment is more sophisticated; stronger, faster and more demanding of fluid. Equipment makers are multinational enterprises who need reliable performance to gain a competitive edge, and also to keep their warranty claims down. And end users expect more return on the capital they sink into equipment – better fuel consumption, higher output, zippier cycle times.

This means lubricant blenders can at last move customers up the scale in terms of the fluid they buy, asserts RohMax Oil Additives. RohMax, part of the German chemical giant Degussa AG, is a longtime believer that high viscosity index hydraulic fluids based on shear-stable viscosity index improvers make a positive difference in hydraulic fluid performance. For the past few years it has been talking up this message with lubricant blenders, equipment makers and end users alike.

Whats been happening with hydraulic equipment in the field is that systems are being designed to be more efficient, more compact, with more pressure and speed. Fluids are subjected to higher temperatures, pointed out Doug Placek, business development manager at RohMax in Horsham, Pa. All this is being done to squeeze more efficiency from the design – and it places additional stress and performance challenges on the hydraulic fluids.

What RohMax has done, Placek said, is identify an actual performance benefit, where the fluid contributes to the overall hydraulic system performance.

RohMax calls such fluids MEHF, for Maximum Efficiency Hydraulic Fluid. Tied closely to fluid viscometrics, MEHF is a performance standard that quantifies the gains that high viscosity index hydraulic oils can offer – no matter what type of pump theyre used in. Equipment manufacturers are paying attention, says RohMax.

Weve developed a very close relationship with major pump manufacturers, who have been very concerned about shear stability for a long time, about the increasing temperatures and pressures the oil has had to work under, related Mike Zink, RohMaxs global business manager for hydraulic fluids. The next step was to show how the fluid could contribute to hydraulic system efficiency – which is a major performance target for most equipment builders.

Efficiency can be manifest in several ways, he continued. Maybe its fuel cost, or equipment productivity, or for others, reducing emissions. In terms of equipment, it may mean getting more power output from a smaller unit. It varies from company to company and country to country. In North America, for example, end-users appear to be looking for increased productivity. In Europe, energy costs are a first concern, and in Asia, its emissions reductions. MEHF offers all of these benefits.

MEHF is not an additive package – thats a common misconception – but rather its a performance-level definition for hydraulic fluids, Placek emphasized. However, modern viscosity index improver additives allow a hydraulic oil to achieve the fluid viscometrics required to meet the MEHF performance level.

The advantage to the oil marketer, Zink noted, is that theres no one additive or feature they have to select for promotion. It allows for a flexible marketing approach, that can offer real value for every type of end user.

Five Points Better

To meet the performance level as it is defined, youll need a certain viscosity index and shear stability, Placek explained. For example, with an ISO 46 grade fluid, you need to formulate to a viscosity index greater than 150 with very good shear stability. Such a fluid will be capable of delivering a 5 percent efficiency benefit or better. And the gains can even be pushed to two digits in a wide number of applications.

Fluid temperature plays a crucial role in the MEHF concept, as RohMax defines it. The fluid temperature can range widely over the course of a single day of operation, and likely will be different for different pieces of equipment as well. As ambient temperatures drop, viscosity will rise and, on start-up and warm-up, lead to poor flow to lubricated areas, draining energy. One solution is to use a lower viscosity oil to improve the low temperature pumping efficiency, said RohMax, but if the viscosity then becomes too low at the higher operating temperatures, too much fluid slips past the moving parts of the pump, decreasing the efficiency of the hydraulic system. Film strength may also be lost, resulting in high wear rates, reduced equipment life and equipment overheating.

To address both of these problems, a high viscosity index fluid (one with a lesser response of viscosity to temperature) is needed. RohMax estimates that by increasing a fluids viscosity index from 100 to 150, another 10 to 15 degrees C of operating temperature range can be gained. This higher V.I. fluid – that tolerates both higher and lower temperatures while maintaining the same viscosity range – can also service a wider range of equipment and pump sets, an important benefit for operators of mixed fleets of equipment.

To define MEHF performance, RohMax has developed a standard protocol in a Denison T6 vane pump. Results in this test show that as the viscosity index increases, the efficiency advantage also increases, Zink said. These efficiencies can be seen by blenders, equipment operators and OEMs by using a calculator available on the www.mehf.com website. Here, users can enter their own gear or vane or piston pump type, and see the potential gains as V.I. is pushed past 100, to 160, 180 or even to 200.

RohMax and Japanese equipment maker Komatsu have delivered joint papers on the MEHF concept, and other OEMs are also said to be looking closely at the data, although none has formalized MEHF in a written specification yet.

Getting on Board?

According to the National Petrochemical and Refiners Association, hydraulic fluid sales in the United States in 2004, including fluids for industry and mobile equipment, fire-resistant fluids, and tractor hydraulic/transmission fluids, totaled some 270 million gallons. Thats far less than engine oil, but it still accounts for nearly one in every 10 gallons of lubricant sold.

Trying to push more of this market into a higher-value tier is taking concentrated effort, pointed out Steve Tillery, RohMaxs regional sales manager for North America. We have done a lot of homework here. We talked to technical, business and hardware persons to get different viewpoints. We have excellent theory and have published widely. Weve taken MEHF into a number of pump testing situations, types and applications. Soon we will be publishing the results of a limited field test, which confirms our laboratory and test rig findings in the field. Weve been surveying end users, asking them what they like and so on. And were taking all that data to our blender customers.

Superior, Wisconsin-based Amsoil Inc. looked closely and liked what it saw, said Kevin Dinwiddie, technical products manager there for drivetrain and powertrain. The independent blender uses polyalphaolefin base stocks to make its Amsoil AW series hydraulic oil, and its sales literature now trumpets the MEHF label and benefits. The company boasts of having the first synthetic MEHF fluid in the world.

The hydraulic oil we had in our product line – formulated by Alan Amatuzio and the guys in our lab – already met the basic MEHF requirements, Dinwiddie told LubesnGreases, but Amsoil worked with RohMax to kick up the fluids viscosity performance. In our case, we didnt have to use as much viscosity modifier as fluids that are made with Group II or II+ base stock. And now we are seeing even greater benefits than the others, even given the greater cost of PAO, he said.

Dinwiddie said customers in the United States still seem to be very cost-driven. It may not be in their budget to pay more to gain these benefits. But a lot of them do have the money to do it, and our research shows that 15 to 20 percent of customers are willing to pay more for the fluid to get better performance. Fact is, the mechanical efficiency on equipment cannot be improved, so the fluid is one thing that they can use to get better efficiency.

Because of gasoline prices being so high, everyone is interested in better fuel efficiency. Using a better hydraulic oil goes straight to the bottom line, whether youre an independent operator or someone with 50 trucks or a city fleet.

Converts in Canada

Petro-Canada Lubricants also is making MEHF fluids. Tanvi Bhatt, category manager, hydraulics, in Mississauga, Ontario, says that its MEHF-type products include Hydrex XV, Hydrex Extreme and Produro TO-4 Synthetic All Season. All wereintroduced fairly recently, within the past four or five years. Hydrex XV is a true MEHF product, she added, with wide application for mobile hydraulics such as those used in the forestry, construction, mining and marine industries.

There are three main issues that may drive an end user to a higher-performance fluid, Bhatt said. Theyll ask, Is this an OEM requirement? Do I want my equipment to see less wear? And whats the cost to replace this equipment?

To answer these questions, Petro-Canada developed a calculator for its distributors and sales representatives to use with customers. We can show that the savings using MEHF-type fluid versus ATF, say, can average 5 to 15 percent in efficiency. Theres still a market for ATF in hydraulics, and will continue to be, Bhatt conceded. The hydraulic market as a whole is very commoditized. Thats where this cost-savings model is very useful. To sell a specialty hydraulic fluid you have to do a lot of homework with the customer.

The ideal candidate for Hydrex XV, she said, is one who requires a high V.I. lubricant that is suitable for a wide temperature application – whether its in western Canada, the Middle East, or Europes norther tier.

Its not a low-cost fluid, though. Yes there is a market for that, but Petro-Canada doesnt want to play in that area, Bhatt said. Weve promoted Hydrex XV as an all season premium product, providing highest productivity year-round. We do not use the term MEHF per se, however. Our positioning for Hydrex XV is to focus directly on the products benefits.

Dave Dragert, R&D product specialist at Petro-Canada pointed out that only Petro-Canadas own high-quality Group II+ and Group III base oils are currently used in developing its products.

Beyond the higher V.I. recommended by RohMax, Petro-Canada also made improvements to the fluids oxidative stability and thermal stability to extend the oils life, that is, to retain its fresh oil properties longer, he stated. With some input from RohMax on selecting the components, the development of the fluids was Petro-Canada driven.

Bhatt praised RohMaxs initiative with MEHF. One of our biggest challenges is to tangibly show that we are generating maximum value for our customers. However, Petro-Canada has been extremely successful, and with the help from RohMax we have developed a robust cost-savings model that translates energy efficiency into real savings.

Polymer Potential

Is this an altruistic project? Well, clearly theres something in it for RohMax as well, Mike Zink remarked. The way to greater efficiency is to have a high viscosity index fluid that is also highly shear stable; that cannot be separated from the definition. And RohMax is the leading supplier of shear-stable viscosity improvers. Most formulators will need these products to meet the MEHF standard.

RohMaxs core technology is polyacrylmethacrylate (PAMA) polymers, which Zink calls a highly customizable product chemistry, which can be very finely tuned for the customer to deliver the rheological features they want in their fluid.

There are a number of polymer technologies out there, and some of the others are more thickeners than viscosity index improvers, said Doug Placek. They thicken the fluid at both high and low temperatures. But with PAMA you get less impact at low temperatures. In colder climates a high percentage of fluids have been based on PAMA due to their good low temperature start-up properties. Now were also emphasizing the efficiency benefits on the higher temperature operating side as well.

The tradeoff, he allowed, is financial, because the fluid costs more, but this minor cost increase is quickly paid back.

Zink sees other additive companies joining the efficiency bandwagon, too. Theyve seen what weve published and recognize the value, he said. We think theyre supportive because they see the growth potential in high V.I. hydraulic fluids. RohMax is in the right place to quantify these benefits … and were definitely the leading supplier in shear-stable viscosity modifiers.

Above all, we want to see this performance advantage take hold of the market and grow. And obviously we all benefit if that happens.