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With international emissions and efficiency targets rapidly approaching, the pressure on automotive engineers has never been higher. The European Union\u2019s (EU\u2019s) 2021 target limits carbon dioxide emissions to 95 grams of CO2<\/sub>\u00a0per kilometer for passenger vehicles, while the 2030 target aims to reduce the same measure by an additional 30%.<\/p>\nTightening efficiency regulations can only energize the consumer market for hybrid and electric vehicles, and so far, the EU\u2019s forecasts suggest this is indeed the case. But as Ishikazi and Nakano1<\/sup>\u00a0report, \u201calthough the automobile market is shifting to electrification, in 2030, vehicles equipped with internal combustion engines will still account for approximately 90% of the annual sales volume of passenger vehicles.\u201d In other words, combustion engines that do meet the new EU standards for efficiency will still be in high demand.<\/p>\n Whether the power source is an internal combustion engine or an electric motor, the overall efficiency, in terms of emissions, must improve to meet these new standards. For this purpose, formulators are increasingly turning to ultra-low viscosity oil, which improves fuel economy, though not without a host of knock-on effects throughout the drivetrain.<\/p>\n These new ultra-low viscosity oils will have to protect the components of the fuel-efficient drivetrain without affecting its fuel economy. \u201cEnergy efficiency is rapidly changing lubricant formulations. The lubricant is being asked to do a lot more with less,\u201d says STLE-member Donna Mosher, technical support manager for transportation lubricants at BASF. \u201cNew gear-train designs are using less oil, operating at higher loads and hotter temperatures, and oil drain intervals\u2019 demands are extending. The oil formulation is changing to address these new designs.\u201d<\/p>\n Viscosity and the Stribeck curve<\/strong> Among other factors, Mosher recommends considering the downstream impacts of lowering a lubricant\u2019s viscosity on the oil drain interval (ODI). \u201cIf the oil viscosity is too low and the efficiency decreases due to more asperity contacts, the wear will increase,\u201d as will the lubricant\u2019s temperature, potentially compromising both component life and the overall ODI.<\/p>\n The operational needs of the application also must be taken into account, as some systems are prone to respond differently to certain oil types over time, says STLE Vice President Dr. Ken Hope, global PAO technical service manager at Chevron Phillips Chemical. \u201cFor instance, does the base oil have a tendency to absorb or shed water? Would the viscosity properties be subject to change given shear, absorption of moisture or process components? Looking at the lubricant as a system of component parts and the interplay of those parts within the intended application is key to designing the most efficient lubricant.\u201d<\/p>\n Prospector has hundreds of materials from global suppliers. Find technical data, promotional material, supplier contacts, and more in Prospector.<\/p>\n Formulating efficiency<\/strong> Switching oil types without assessing the possible downstream effects on all components risks trading small inefficiencies for much larger ones, given the limited role of gear lubrication in emissions levels. A historical review by STLE-member Mark T. Devlin in 20182<\/sup>\u00a0found that vehicle energy loss due to friction in the engines, axles and transmission accounts for only 5%-15% of fuel combustion energy, while the rest is unaffected by gear lubricant formulation, though future advancements within the drivetrain might increase this limited impact.<\/p>\n Over the past five years, says Mosher, new drivetrain configurations have poured into the market, all featuring widely varying approaches to the structural challenge of fuel-efficient design. But focusing the fuel economy conversation on the drivetrain alone sidelines an opportunity to incorporate best practices in lubricant formulation. \u201cThese new drivetrain configurations tend to focus on the gearbox design, with lubricant sometimes being an afterthought,\u201d says Mosher. \u201cBy bringing the lubricant formulation into the gearbox design early in the design process, collaboration results in gearbox design selection, [leading to] improved efficiencies.\u201d<\/p>\n Chemistries of the future<\/strong> Despite the complexity of the Stribeck curve, Ishikazi and Nakano forecast that, on the whole, \u201cthe viscosity of mineral engine oil is expected to continually decrease in the future,\u201d as the consumer market increases pressure to invest in electric motors and their lubricants.<\/p>\n \u201cThe popularization of synthetic engine oil as we move toward 2030 will require the consideration of both the reduction in viscosity and the extension of the oil drain interval,\u201d write Ishikazi and Nakano. As manufacturers scramble to keep up with regulations and consumer demand, \u201cthe largest challenge I see is the speed of change,\u201d says Mosher.<\/p>\n Excerpted and reprinted with permission from the September 2020 issue of Tribology and Lubrication Technology<\/em><\/a> (TLT), the official monthly magazine of the Society of Tribologists and Lubrication Engineers, an international not-for-profit technical society headquartered in Park Ridge, Illinois..<\/p>\n Lynne Peskoe-Yang is a freelance writer based in Tarrytown, N.Y. You can contact her at\u00a0lynnepeskoeyang@gmail.com<\/a><\/p>\n
\nThe Stribeck curve, which estimates the friction coefficient of a given system as a function of lubrication viscosity, suggests the general rule that lower viscosity in a gear lubricant contributes to higher efficiency, but knowing this rule is insufficient. Driving cycles, vehicle condition and control systems can all trigger changes in temperature, shear and pressure on the lubricant that fall outside expectations predicted by the curve. \u201cSimply changing the viscosity of the lubricant to gain efficiency can rapidly result in early failures,\u201d warns Mosher. Intimate knowledge of the application and oil formulation also are essential, as \u201cviscosity is just one parameter that is used for efficiency,\u201d says Mosher.<\/p>\n
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\nRegardless of the formulator\u2019s personal or institutional commitment to fuel economy, a lubricant can only stretch as far as the laws of tribology permit. Ishikazi and Nakano recommend that designers consider the full life cycle impact of their oils and additives, as the emissions released during production can vary widely depending on the oil type and manufacturing plan.<\/p>\n
\nFormulators have no choice but to adapt to necessary regulations, but R&D investment will likely expand to meet this need. The rapid shift to electrification in vehicles will encourage \u201cdiversified investment in a number of technologies, including vehicle electrification, autonomous driving and artificial intelligence,\u201d predicts Ishikazi and Nakano.<\/p>\n
\n1. Ishikazi, K. and Nakano, M. (2018), \u201cReduction of CO2<\/sub>\u00a0Emissions and Cost Analysis of Ultra-Low Viscosity Engine Oil,\u00a0Lubricants,<\/em>\u00a06<\/strong>\u00a0(4), 102, Doi:10.3390\/lubricants6040102.
\n2. Devlin, M. T. (2018), \u201cCommon Properties of Lubricants that Affect Vehicle Fuel Efficiency: A North American Historical Perspective,\u201d\u00a0Lubricants,<\/em>\u00a06<\/strong>\u00a0(3), 68, Doi:10.3390\/lubricants6030068.<\/div>\n
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\nAbout the author<\/h3>\n
About STLE<\/h3>\n
![\"Society](\"https:\/\/ulprospector.ul.com\/media\/2018\/03\/STLE_logo.png\"){kind=logo}
The Society of Tribologists & Lubrication Engineers (STLE) is the premier technical society serving the needs of over 12,000 individuals and 250 companies and organizations that comprise the tribology and lubrication engineering business sector. STLE members are employed by the world\u2019s leading corporations, academic institutions and by governmental agencies dealing with science and technology. STLE supports these distinguished technical experts with a variety of professional education and certification programs.<\/p>\n","protected":false},"excerpt":{"rendered":"