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Better Lubes, and Fewer


WASHINGTON, D.C. – Drivers of General Motors 2005 model year vehicles equipped with its engine Oil Life System – and nearly all of them have this onboard technology – will typically be able to go 8,500 miles between oil changes, an executive with the company said last month. Whats more, drain intervals beyond 30,000 miles and even 40,000 miles are well within reach, he added confidently.

Drain intervals are a very specific goal for GM, and are being managed in a logical and planned fashion, according to the companys James A. Spearot. Longer drain intervals are desirable to meet customer demands for reduced maintenance and convenience, and for the environmental benefits that come with less oil handling. And in the end, longer drain intervals will help us with our warranty protection goals.

Spearot is director of the Chemicals and Environmental Sciences Laboratory at the General Motors R&D Center in Warren, Mich., a position hes held since 1998. He is also a past chairman of the SAE Fuels & Lubricants Committee, and was involved in advancing the GF-series engine oils that GM and other U.S. and Japanese automakers recommend in their owners manuals today. He spoke here Sept. 15 to the World Tribology Congress, which was jointly sponsored by the American Society of Mechanical Engineers, the Society of Tribologists and Lubrication Engineers, and the International Tribology Council.

GMs proprietary Oil Life System tells the driver when its time to change the oil, using a color-coded system, he explained. A yellow condition alerts the driver that its time to think about changing the oil; red warns the driver to stop the vehicle because the oil is not suitable for continued service, and may result in damage.

The savings for GM customers going forward will be enormous, Spearot noted, especially compared to competitors, whose intervals still average only 5,000 miles. Over the life of the vehicles, this represents a savings of 6.6 million gallons of engine oil and $145 million dollars for our 2005 model-year customers.

That 8,500-mile figure was based on data from GM dealers on actual drain intervals for vehicles equipped with the Oil Life System, most of them using GF-3 engine oils, Spearot later explained to LubesnGreases. The oil life may be even better now with the new GF-4 engine oils, he added. Today, with engine oils meeting the most current oil specifications, and using synthetic base stocks and existing engine technology, we believe on average our customers could achieve drain intervals of 20,000 miles.

Spearot emphasized that these are average intervals, not absolutes. We still find people who drive severely enough that the Oil Life System monitor goes off at 5,000 miles. But average also suggests that many will surpass that figure.

With improvements in the oil and only minor changes in engine technology, he reiterated, average drain intervals of greater than 30,000 miles will soon be possible. And with some major engine modifications, the average interval will break the 40,000-mile barrier.

We will not do this precipitously, Spearot assured the Washington audience, stopping short of offering a timetable for the changes. We still need to strive for fuel economy, durability and no impact on emissions control systems.

Other vehicle lubricants are also advancing these goals for GM, he said:

Regarding automatic transmission fluids, there is a new factory-fill product for 2006 vehicles across GM worldwide. This product, trademarked as Dexron-VI and unveiled on April 1, has twice the friction stability of Dexron-III (the fluid it is replacing) plus improved oxidative stability. Spearot praised the oil and additive industries for creating the improvements which enable Dexron-VI to be a fill-for-life transmission fluid capable of

going 100,000 to 150,000 miles in all applications, no matter what the driving regime. Dexron-III fluids will not be licensed after 2006, he added, allowing Dexron-VI to take their place throughout the aftermarket as well as in factory fill.

In the area of rear-axle lubricants, weve gone to recommending an SAE 75W-90, a lower viscosity oil that gives a 0.6 percent improvement in fuel economy versus using an 80W-90, Spearot said. This modest-sounding change delivered better oxidative performance and oil life, too. To our surprise, we also got lower operating temperatures in the rearaxle sumps with the new oils, as much as 15 degrees lower.

The company is also looking at greater use of synthetic base stocks in order to improve lubricant life and viscosity characteristics. As much as possible, we want to use lubricants as a system component, rather than as consumable items that need to be added, he said.

Spearot does not lay every improvement at the door of better lubricants, however. In many cases, tribology – the science of rubbing surfaces – deserves the credit. For example, GM wanted to use low-viscosity gear oils to gain fuel efficiency, but it found that the oil film thickness was less than the surface roughness of some moving parts. Rather than boost the oils thickness and sacrifice fuel economy, GM applied a coating of chromium nitride to the gears mating surfaces. This self-polishing coating reduced surface roughness and formed a durable film that protects the gears. The low-vis oil then worked fine to cool and lubricate.

Spearot also discussed the lubricants – metalworking fluids, rolling oils, stamping and forming lubes and more – that are used in GMs plants and processes. These fluids need to be seen in the context of todays automobile industry, a dynamic industry characterized by rapid growth and increasingly global competiiton.

What is it the auto industry sells? he asked the nearly 900 scientists, researchers and engineers who attended the event. Is it cars? Ninety-five percent of people would say so. What we really sell, though, is automobility, the ability to move around at will. Once humans are past the basic needs (food, shelter, society), they seek the gratification of being able to move around, he said.

This human drive can be seen in the strong link between personal vehicle ownership and overall economic health, he said, pointing out that in 2000, 12 percent of the worlds roughly 6 billion people had the advantage of personal transportation. The strongest economies – the United States, Japan, Germany – are also the ones that enjoy the highest rates of vehicle ownership.

The rest of the world is catching up, though. By 2020, General Motors forecasts, the global population will have grown to 7.5 billion people, and about 15 percent of them will have personal transportation. That is, there will be more than 1 billion vehicles on the planet – with all the good and bad that implies.

Spearot outlined five major areas where this boom in vehicle ownership will present challenges, the first two naturally being energy and the environment. Safety is another (particularly in developing countries where the road system is not safe and well-constructed), and congestion a fourth area of concern, as more of the population concentrates in urban areas. Affordability, he added, is the final critical challenge. The auto industry must be able to sell vehicles in those places where people are beginning to be part of the middle class

Resolving nearly all of these challenges will depend to some degree on tribology: Energy and the environment will be addressed with advanced propulsion systems, alternative fuels and advanced materials, such as new lightweight alloys and more durable coatings. Safety will be improved through vehicle electronics, controls and software. And even congestion may be improved through the careful and appropriate use of on-board telematics. And a good part of affordability will be addressed by processes such as agile manufacturing, he continued.

To improve manufacturing productivity and environmental compliance, to boost fuel economy and maintain emissions, we need to take weight out of the vehicles, such as through the use of light alloys. For example, like most automakers GM machines its engine blocks from aluminum alloys, adding a cast-iron liner for the combustion chamber. But there are problems with using cast-iron liners, from their weight, to manufacturing, to recycling after the vehicle is scrapped. Alternatives are still being sought, but tribology will surely play a part in the search.

For vehicle bodies, of course, GM has been adopting lighter materials for years, first aluminum and then magnesium alloys, and finally powdered titanium metals, requiring new processes. One of these, quick plastic forming (QPF) was introduced at GM just two years ago, and allows more complex parts to be formed rapidly from sheets of aluminum, including, Spearot pointed out, the lift-gate panels of the companys Chevy Malibu

Maxx. Previously, such a complex shape required numerous steps to form steel and aluminum parts, plus another step to join them securely. Now, the entire outer panel is created from aluminum in one

step, minimizing labor and material costs. It cut the parts weight, too, from 39 pounds to 20 pounds.

QPF depends heavily on tribology, Spearot added, which governs the formability, cycle time, durability and wear, and surface quality of the finished part. With aluminum, any irregularity between the die and blank reads through to the formed part, he explained, and will appear as blemishes on the parts surface. Particles may accumulate on the die during the forming process, especially if theres not a suitable lubricant there, which leads to galling. The coefficient of friction must be controlled carefully, especially to avoid deformation during the stretching of the sheet. GM is seeking a good test that matches the actual QPF manufacturing processes, such as the stretching action, so the lubricants and coating processes can be evaluated and improved.

One issue with QPF is that it requires pre-heating of the blank, so the lubricant – in addition to reducing the coefficient of friction, improving formability and die life, cutting cycle time and facilitating die release – is expected to help shorten the pre-heating cycle. So far, results have been good using a coating of boron nitride, which is easy to clean and a good lubricant, Spearot said, but it suffers from a high cost. By comparison, graphite is a good lubricant and is low in cost, but is not easy to clean from the formed part.

QPF also presents application issues, since the forming lubes must be sprayed on the sheet metal (expensive) or brushed or rolled on (slow), and uneven application creates headaches. The ideal lube, he added, would also be compatible with the welding/painting steps that follow the forming process, in case not all of the lubricant is cleaned from the surface.

Wet machining is another ongoing issue with lubricants on the manufacturing floor. Mist is a major health and safety issue in the plants, yet most machine operations generate centrifugal mist. Additionally, high-speed machining operations make centrifugal mist and can also vaporize the coolant, so it condenses into small particles at submicron size, Spearot said. Were looking at the impact of the lubricant type and how it affects mist. Vegetable based coolants, for example, seem to have high centrifugal mist but very low condensed mist. Reducing the Noack volatility and increasing the flash point of the fluid can also reduce condensed mist, GM has found.

But all else associated with machine fluid is burdensome, he stated flatly, so were looking at dry machining. The biggest obstacle so far, he added, is the slowness of dry machining. This is where fluid lubrication really shines. In a typical drilling operation using conventional wet machining, 10,000 parts might be manufactured

before a tool change is required. With dry machining, we can barely make 10 parts before it can destroy the drill, Spearot said wryly. GM has tried using diamond or diamond-like coatings on the carbide drill tip and has seen some improvement: up to 2,000 parts dry machined before tool changeout was needed. So its going to be some time before fluid machining ends.

Eventually though, he feels that this challenge will also yield to tribology. Auto manufacturing, he stated confidently, is on the cusp of a tribology renaissance.

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