Low Viscosity Engine Oils

These lubricants provide better fuel economy, plus other benefits


Late last year, a collaborative effort between research teams in England at Shell Lubricants and automotive design company Gordon Murray Design (GMD) led to the development of an innovative concept engine lubricant capable of achieving a 6.5 percent improvement in fuel efficiency.

This is “a step change compared to the improvements of around 2.5 percent achieved in typical fuel economy lubricant development programs,” says Selda Gunsel, Shell Lubricants’ vice president of lubricants and B2B products technology.

Using GMD’s new T.25 city car as the test bed, Shell engineers were able to work beyond current industry specifications to formulate an ultra-low viscosity 0W-10 engine oil for even greater efficiency.

The T.25 is an ultra lightweight, compact car, about half the size of the average car. It was designed to have world-leading efficiency and ultra-low emissions, according to the company, and is optimized for performance, cost, safety, usability, recyclability and ease of assembly.

RESISTANCE TO FLOW

An oil’s viscosity – a measure of its resistance to flow, along with the pressure and speed of movement, determines the thickness of the oil film between two moving surfaces. This, in turn, determines the ability of the oil film to keep the surfaces apart, the rate heat is generated by friction and the rate the oil flows between the surfaces to convey the heat away.

Changes in an engine oil’s viscosity can affect the oil’s lubricating (protecting) ability. If too thin - having a low viscosity; or too thick - having a low viscosity - more friction and drag will be created, resulting in premature wear and failure.

NEW STANDARDS

Changes in legislation and new emission standards are putting pressure on vehicle manufacturers to improve fuel efficiency and reduce emissions.

While the development of increasingly fuel efficient engines is ongoing and has made significant progress in recent years, lubrication is one area that can provide an extra boost to help meet those targets.

The co-engineering approach between the Shell and GMD development teams used sophisticated mathematical modeling techniques to define the optimum lubricant for the T.25 engine design, helping to achieve the lowest possible engine friction, Shell’s Gunsel says.

“Blending low viscosity oil to improve fuel efficiency is actually relatively simple,” she notes. “The challenge comes when you look to balance it with engine protection and acceptable oil drain intervals.

Although in the concept stage, the 0W-10 engine oil “represents a major advancement in lubricant technology.”

“Of course, engine oil is just one part of the fuel efficiency story,” continues Gunsel. “But when we take into account the pressure and incentives for vehicle manufacturers to reduce CO2 emissions, the contribution from lubricants can become very significant.

“This is due to the fact that with less engine friction comes less fuel use and, ultimately, less CO2 is emitted.”

DESIGN PROCESSES

“We have challenged every aspect of car design to create the T.25 and the environmentally positive iStream design process, and the lubricant is no exception,” says Professor Gordon Murray, GMD’s CEO and technical director.

The iStream “is a complete re-think on high-volume materials and the manufacturing process, and will lead to a significant reduction in CO2 emissions over the lifecycle of the vehicles produced using it, compared with conventional ones,” he explains.

Using the new Shell 0W-10, the T.25 achieved 96 mpg in the Royal Automobile Club Future Car Challenge, winning the award for the most economic small, passenger internal combustion engine vehicle.

The annual event is designed to demonstrate, promote and challenge the development of new-energy and related technology for tomorrow’s highways.

 

The 6.5 percent figure was derived from testing on an urban cycle (designed to mimic the conditions of city driving). Combined cycle (designed to mimic both urban and highway driving) testing yielded a 4.6 percent benefit. The testing undertaken compares the concept lubricant to a 10W-30 oil which is a widely used viscosity in European markets.

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