Driveline Lubricants – Location Matters

It would be easy to assume that the requirements for commercial vehicle driveline lubricants are the same throughout the world, but nothing could be further from the truth.

Specifying the right type, grade, formulation and quality of gear oil for axles and manual transmissions in commercial vehicles is essential to ensure the best possible fuel efficiency and maximum durability for gear components. But the stark reality is that there are huge regional differences in the types and quality of fluids used throughout the world, sometimes leading to both inadequate protection of expensive equipment and increased fuel consumption. This may happen because the ideal specification of fluid is hard to come by, or through a desire to save money by using cheap, though often inferior, products. Fluids can also be wrongly applied through habit, or failure to understand the substantial longer-term benefits of using the latest gear oil specification.

Lubrizol is continually striving to educate and inform commercial vehicle operators of the importance of choosing gear oils carefully, to ensure adequate protection while reducing internal friction in the driveline and improving fuel consumption. This process of enlightenment is made more difficult because the starting point is lower in some markets than others. In the US and Western Europe, the importance of using fluids precisely specified by the vehicle and driveline manufacturers is well-understood. So, too, are the benefits of remaining current with the latest generations of fluids as they emerge. But the story is less encouraging elsewhere in the world. In Eastern Europe, India and Asia, for example, the baseline is set much lower and the step up to using the latest fluids, that much higher. In some instances, operators are even known to use engine oils for driveline lubrication on a “one fluid suits all” basis. Although providing excellent lubrication in engines, engine oil is totally inadequate for axle lubrication and rapidly changes its viscometric profile during use.

Fluid Standards — Raising the Game
Part of the problem lies in understanding the limitations of existing fluid standards. Two of the most widely-known standards for gear oils are API GL-4 and API GL-5. Both are widely regarded in some parts of the world as a satisfactory validation for driveline fluids, but in fact they only signify that a product meets the most rudimentary standards. API GL-4 is now widely regarded in the industry as obsolete and the tests required to approve a fluid for GL-4 are no longer available. Today, the game has moved on and both vehicle and transmission manufacturers are working closely with driveline fluid additive manufacturers. Together, they develop dedicated gear oils which offer the maximum protection, extended drain intervals and reduced fuel consumption through a process of extensive laboratory and field testing. Many OEMs develop specific formulations of driveline fluids in conjunction with additive manufacturers, to suit individual transmissions and vehicles.

A complex and thorough series of tests is used to approve driveline fluids for use with specific equipment, covering crucial physical aspects such as viscometrics, thermal properties and shear stability. Once a fluid is approved, it will not be changed without going through the entire approvals process all over again. One thing that all new fluids have in common are greater durability with improved thermal stability, much longer drain intervals, lower viscosity for reduced drag and increased fuel consumption, and reduced cost. Given the potential consequences for heavily-stressed costly gear components, using inappropriate fluids for short-term cost savings does not make much sense.

New Fluids, New Capability
In Western Europe and North America, the trend is toward new, robust, lower viscosity fluids, such as SAE 75W-80 grades in manual transmission factory-fill and SAE 80 or SAE 80W-90 in service-fill applications. Similarly, in axles, the industry is moving toward SAE 75W-90 for factory-fill and SAE 80W-90. These lower viscosity fluids are further evolving into SAE 75W-85 for even better fuel economy.

However, with the pressure on to cut costs, commercial vehicle fleet operators do not always appreciate the longer-term savings they might have when it comes to durability of components, fuel savings and extended drain intervals. In emerging markets, traditional, less efficient, heavier viscosity grades are still widely used as a matter of course, due to availability, slightly lower cost and familiarity with the products.

Location and Environment
Geography and climate have a major impact on the performance of driveline lubricants and it is important to choose the correct fluids for the topography and ambient temperatures a vehicle is operating in. The demands made on a vehicle’s driveline regularly traversing mountainous regions will be very different to those encountered by another which spends its life travelling largely on flat roadways.

Similarly, short-haul operations imply frequent stopping and starting, exposing the driveline to a completely different duty cycle than would be experienced in long-haul, trans-continental operations. So, components are influenced by the load the vehicle is carrying and the distance travelled, as well as temperature and topography. Increasingly, modern trucks are being equipped with intelligent service interval management systems, which tell the driver when services are approaching and these systems assume that the fluid in use matches the manufacturer’s specifications. If an inappropriate or inferior fluid is used, the driveline may suffer from durability problems.

Ambient temperatures vary considerably in different regions across the globe and modern, wide-span multigrade lubricants have been designed to support these differences under SAE J306 guidelines. When running in a hotter climate, the conventional approach is to use a thicker fluid. In a cooler climate a thinner fluid is more appropriate to flow well at lower temperatures, but it should still be capable of providing maximum protection to the driveline components.

What Do the Labels Mean?
The first number in the SAE label for a multigrade is suffixed by a “W” for winter, such as SAE 70W, 75W, 80W or 85W. This represents the fluid’s ability to flow in winter temperatures, so the performance of 70W is measured down to -55°C, 75W at -40°C, 80W at -26°C and 85W at -12°C.

The second number represents the kinematic viscosity in summer temperatures and is measured at 100°C. In Europe, the kinematic viscosity of a fluid would typically be established at around 15 cSt (Centistokes, a measure of kinematic viscosity) for axles and about 9.5 cSt for manual transmissions. These figures may be adjusted up and down respectively for maximum protection in more extreme climates. However, maintaining sufficient protection for components when viscosity is lowered requires the use of more effective additive packages, and only then can an effective blend of performance and durability be achieved. Lubricant chemistry is a highly complex and technical subject, and one which emphasizes the importance of choosing the right fluid for given conditions and duty cycle.

axle-fluid-trends

Additive Components
Detergent

Neutralises oxidation by-products.

Oxidation Inhibitors

Prevent oxidation which produces acid, sludge, varnish, thickening and decomposition of the oil. Combats the main causes which are temperature, catalysis by metal ions, oxygen and NOx.

Corrosion Inhibitors

Factors affecting rust and corrosion include the nature of the metal oxide, the presence of a solvents like water, salts, acids, alkalines and temperature. Inhibitors neutralize acid and prevent the formation of film.

Friction

Friction inhibitors take the form of straight-chain and fatty-acid molecules which reduce friction between the two metal surfaces.

In the US, the pattern is similar, with approved fluid use reaching 59%, extended drain fluids of some sort used by 36% of the market and only 5% using basic fluids. Japan is best of all, with 85% of the market using an OEM-approved fluid. In Brazil the situation is not so good, with 44% using OEM-approved fluids and 48% using basic API GL-4 and API GL-5 fluids. Only 8% not in the first group are using some sort of extended drain fluid.
(Source: Lubrizol-commissioned market research)

Russia, China and India give most cause for concern. Restructuring of the Chinese industry has a part to play in this. Factories are relocating from the coast to poorer inland areas to take advantage of more favorable labor rates. Small trucking companies are overloading vehicles to try and maintain profit margins because rates for carrying freight have remained fixed, despite the extra distances covered. It also means that owner-operators are forced to compromise on maintenance in order to save money.

In Russia, 41% of the market uses OEM-approved fluids, largely due to the influx of Western European equipment. In India, it is thought that only 10% are using the approved fluids, with 70% using basic fluids and 20% extended drain, validated products. The story is similar in China, with 80% using basic fluids, 10% using an OEM-approved fluid and another 10% using a high quality, extended drain fluid of some sort.

axle-fluid-trends-2

The Americas: A Different Ball Game
Moving from the frozen wastes of Siberia or mountainous regions of the Alps to North or South America might seem to pose fewer challenges for driveline lubricants, but conditions are just as tough on the other side of the Atlantic. North and South America each pose a different set of challenges to both drivelines and the lubricants that protect them. First of all, there are legislative differences that have a bearing on the life cycles of driveline components. In North America, the larger commercial vehicles are typically Class 8 tractor-trailer units (known in Europe as articulated lorries). But there are also around 108 million pickup trucks and SUVs in North America (large vehicles by European standards), which are often subjected to heavy-duty cycles, too.

In North America, a predominant specification for commercial vehicle driveline lubricants is SAE J2360, which today applies to both non-synchromesh manual transmissions and axles. The Class 8 vehicles are usually subject to the OEM’s requirements for performance. In many cases (up to 30% in Western Europe), those fluids are synthetic and certified as extended drain fluids capable of surviving intervals of up to 500,000 miles (800,000 km). Lighter-duty pickup trucks and SUVs are often used by tradesmen for hauling tools and materials, as well as towing trailers and boats, and even for plowing snow. Many of these vehicles undergo severe use and require additional protection. Lubrizol’s new Towproof™ technology is an example of how new additive packages are being developed to respond to the needs of both the manufacturers and the end user for service-fill gear oil lubricants used in Class 3 through Class 7 vehicles in North America.

There are, however, key differences between North and South America. In North America, trucks are restricted in weight by law to a gross weight of 80,000 lb, mainly due to safety and in the interest of restricting damage to road surfaces. In other countries, such as Brazil and Mexico, there is no such regulation and it is not unusual for the gross weight of a truck to reach 140,000 lb. This puts a tremendous strain on the vehicle driveline, and is exacerbated by mountainous areas and the high temperatures and humidity.

Equipment varies considerably throughout North and South America, too. While North American operators tend to stick to domestic products in their choice of commercial vehicles, European brands have a much bigger role in South America. This widespread range of equipment type makes it even more important to meet the criteria laid down by the manufacturers in such demanding conditions.

In common with the emerging markets of Eastern Europe and Asia, operators often focus on price rather than performance, and reliance on simple GL-4 or GL-5 specification fluids leads to a high rate of equipment failure in these countries. Moving to SAE J2360 would improve the situation immeasurably, with the savings resulting from reduced wear and tear on vehicles far outweighing a modest additional cost.

manual-transmission

The Way Forward
So, when it comes to choosing driveline lubricants for commercial vehicles, the playing field is far from level. While many end users in the more sophisticated markets are already enjoying the benefits of the latest driveline lubricant technologies, there are still thousands who may not have caught up with the latest trends or realize the longer-term financial benefits of switching to a more appropriate driveline lubricant technology.

Field trials and data compilation play a big part in Lubrizol’s research into driveline lubricant use, and will continue to be used to educate users as to how their businesses can be improved by choosing the correct lubricants for their vehicle fleets. They will also help to evaluate new products, with even more effective additive packages planned for the future in the never-ending process of development.

How Lubrizol Aims to Help Operators Drive Their Maintenance Costs Down
Lubrizol has developed a powerful tool to help vehicle operators see for themselves how correct use of the right driveline fluids can cut their maintenance costs dramatically. The Driveline Fleet Calculator Model calculates the difference in cost between standard fluids and extended drain fluids in real terms, even taking into account the cost of fluid changes and the frequency of changes. It also provides illustrations of cost for higher frequency standard drains and lower frequency extended drains, taking into account their impact on service maintenance costs. This means the operator can look at the overall cost of using the correct, high-quality driveline fluid and compare that to the higher maintenance costs incurred by using inappropriate fluids. It also takes into account the cost of trucks being out of service due to unplanned repairs.

For a vehicle covering 100,000 miles annually, maintenance expenses represent 11.9% of total cost. Driveline fluid maintenance costs represent only 0.4% of the vehicle’s variable costs. Interact with Lubrizol’s unique Driveline Calculator Tool now!

driveline-fluid-maintenance-cost-chart

© 2013, The Lubrizol Corporation

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