Fuel Economy Requires Lighter Oils

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Engine lubricants can help provide fuel economy improvements that are becoming bigger priorities for Asian governments, including India. But that will require lower viscosity oils and effective use of additives such as friction modifiers.

That was the message of S.S.V. Ramakumar, general manager of Indian Oil Corp.s research and development center, during an April 28 seminar preceding the ICIS Indian Base Oils & Lubricants Conference in Mumbai.

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Indias Corporate Average Fuel Economy standards, mandated by the Bureau of Energy Efficiency in February 2014, require the average fuel economy for passenger vehicles to reach 18.2 kilometers per liter by the 2016-17 fiscal year and 22 km/l by 2021-22. The current average is 16 km/l.

Ramakumar said engine oils can help improve fuel economy by reducing the amount of energy losses in an engine. The fuel economy improvements offered by engine oil are relatively small, he said, but unlike other strategies they dont require new engine hardware.

According to Ramakumar, the greatest engine oil contribution to fuel economy comes from reduction in oil viscosity grade. He cited Lubrizol data showing that results on DaimlerChryslers M111E fuel economy test improved between 0.6 percent and 1 percent when switching from a 15W-40 reference oil to a 10W-40 oil. A 5W-30 oil improved fuel economy by 1.5 percent to 3 percent compared to the 15W-40, while a 0W-20 caused an improvement of up to 4 percent.

Other industry insiders have expressed similar views about the gains available from reducing viscosity. Castrol India, which claims nearly 18 percent of Indias automotive lubricants market, says fuel economy benefits can be derived by designing bespoke lubricants.

Use of low-friction lubricants is one of the most cost-effective ways to reduce fuel consumption, Castrol Indias technology manager, Milind Vaidya, told Lube Report Asia. In moving from a thicker conventional oil such as a 15W-40, to a thinner, new generation of oils including 5W-30 or 0W-30, a fuel economy increase of up to 3 percent is achievable, in both diesel and gasoline cars. Castrol expects the viscometric portfolio to increasingly migrate towards thinner oils in India in the near future.

As Ramakumar noted, lighter engine oils – 5W and even 0W multigrades – are already popular in Japan, Europe and North America and are now making inroads in other parts of Asia. But there is a drawback; eventually reducing viscosity increases the risk of engine components coming into contact and being worn.

As fluid films get thinner, the entire load is on asperities [in component surfaces], and thus avoidance of metal-to-metal contact now increasingly depends on lubricant additives, he said. Then the issue becomes wear protection.

Providing wear protection in the boundary lubrication regime is accomplished through the use of chemical additives, such as antiwear agents and friction modifiers. Friction modifiers can also provide relatively large improvements in fuel economy, compared to other types of additives, Ramakumar said, but it is important to find the right friction modifier and determine how best to use it.

Friction modifiers do not all perform the same and must be tailored to the rest of the formulation for optimum results, he said.

Ramakumar added that improvements can also come from changes in viscometrics, which are affected by many factors, including high temperature-high shear viscosity (HTHS), kinematic viscosity, shear stability, cold crank viscosity and base oil viscosity index.

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