Unfortunately, significant gains are hard to come by, especially with engine oils. Various approaches have been investigated, but they generally have resulted in only small improvements – fuel economy increases of around 2 percent or 2.5 percent compared to that achieved using conventional lubricants.

Thats why a recent announcement by Shell Lubricants stands out. In mid-January the company claimed it had developed a concept engine oil that achieved a 6.5 percent fuel economy improvement in a new mini-car.

Shell said the 0W-10 engine oil was developed in collaboration with Gordon Murray Design, a British firm that designed the T.25, a vehicle it describes as a city car. According to GMD, the T.25 attained a fuel efficiency rating of 96 miles per gallon (41 kilometers per liter) in the RAC Future Car Challenge, winning an award for the most economic small, internal-combustion engine, passenger vehicle. When filled with Shells concept oil, the vehicles fuel efficiency was 6.5 percent better than when filled with a conventional 10W-30 oil.

Shell noted that the lubricant is not yet ready for market – that it is currently at the concept stage. Still, it claimed to have made a major advancement, and while it stopped short of promising that it can bring to market a product that yields the same improvement, it did predict that the project will have practical benefits.

What we have learnt feeds into the products we are developing for use in the near future, said Selda Gunsel, vice president lubricants and business-to-business products technology for Shell Lubricants.

Low Viscosity for High Efficiency

Shell declined to discuss the formulary features that enabled the improvement. Presumably, low viscosity played a role.

Blending low viscosity oil to improve fuel efficiency is actually relatively simple, Gunsel said. The challenge comes when you look to balance it with engine protection and acceptable oil drain intervals. Engine oil viscosities have been trending downward in recent years. Not long ago 15W-40 was a popular grade of oil for passenger cars. Today 5W-30s and 5W-20s are gaining prominence, and some companies are investigating 0W grades.

The attraction is obvious. Thinner oils exert less drag on moving parts, resulting in less energy loss and allowing engines to operate more efficiently. But as Gunsel alluded, thinner oils also tend to provide less of a fluid cushion between parts, and some formulators have expressed concerns that the trend toward lower viscosities risks compromising the protection of engine components.

Shell officials suggested that the industry could make greater strides in fuel efficiency without compromising wear protection if organizations that write lubricant standards would eliminate requirements that Shell considers obsolete.

Although many of the specification requirements are necessary, there are some historical requirements that are no longer relevant, the company said in a written response to questions from LubesnGreases. For example tests on engine seals that are no longer widely used in engine designs. By discarding the less relevant requirements there will be more scope for new lubricant formulations to hit greater fuel economy improvements that are so needed by auto original equipment manufacturers.

Questioning Rules

It sounds as if Shell discarded some of those requirements in developing its concept oil – an option it had since it was not seeking specification approvals. It will be interesting to see whether Shell or other companies call for specification changes as part of the push for better fuel economy.

Shell acknowledged that it has not yet conducted wear tests on the oil, though it added that it plans to do so. Its possible that an oils ability to protect a vehicle will depend in part on the vehicle itself. The T.25, for example, is half the size of an average sedan and weighs just 550 kilograms. Presumably its engine need not be exposed to pressures as great as those created in larger vehicles.

Clearly, there are unanswered questions concerning the significance of Shells announcement, and the company itself indicated that more work is needed. Nevertheless, any claims of this much improvement in fuel economy will attract attention in the lubricants industry, and if it turns out to be an actual breakthrough, there will be a lot of sentiment to embrace it.

Even so, in the overall scheme of things, this much fuss over a 6.5 percent improvement once again underscores the fact that lubricants have a relatively small role to play in the fuel economy gains that the automakers must make. If the auto industry is to meet the goals that have been set for it, it must also continue looking elsewhere.