Aussie Light-duty Fleet Shifts to Diesel

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Australias fleet of light-duty vehicles continues shifting from gasoline power to diesel – a trend that will require changes in the engine oils supplied for those vehicles.

The Federal Chamber of Automotive Industries last week issued data showing that 88 percent of the 100,768 light commercial pickups and vans sold in the six months ended June 30 were diesel powered, compared with a 65 percent share for the year 2009 and just 40 percent in 2005.

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Diesel engines require higher performance engine oils than gasoline-powered engines.

The bottom line is that diesel engine oils are formulated differently than gasoline engine oils because of the differences in the combustion process, engine loading and fuel chemistry, said Gary Parsons, global OEM and industry liaison manager at lubricant additive supplier Chevron Oronite.

Diesel engines form more soot and particulates than gasoline engines. Therefore dispersant levels in diesel engine oils are higher than those in gasoline engines in order to prevent the soot and contaminants from agglomerating. Because light-duty diesel-powered vehicles are typically commercial vehicles – which are often on the road all day – the anti-wear performance of the engine oil is also paramount. In addition, diesel engine oil has to combat higher sulfur levels of diesel fuel to neutralize the formation of corrosive acids.

New emission standards have put even more importance on the ability of engine oils to control particulates. This has increased demand for high-performance additives and polymers to formulate oils for diesel engines, particularly in hard-working commercial pickups and vans.

The increased usage of additives in diesel engine oils compared with gasoline engine oils means diesel engine oils tend to be more expensive to manufacture. They are also more expensive to develop, with diesel performance categories typically including more tests than their gasoline engine counterparts, said Chevrons Parsons.

The shift to diesel power could lead Australian vehicle operators to focus more on Europes benchmark ACEA oil specifications, which are defined defined by the European Automobile Manufacturers Association (ACEA).Australia has traditionally relied on the United States-based API standards. However, Europes emissions standards are closer to Australias, and the use of diesel there is also widespread, much more so than in the U.S.

In Europes ACEA system, the C2 and C3 specifications define oils that are suited for diesel- or gasoline-powered are used to diesel passenger car engines like those in the Volkswagen Golf or the BMW-3 series. The C designations indicate oils that contain low or medium levels of sulfated ash, phophorus and sulfur, referred to collectively as SAPS, all of which can compromise air emission control devices.The older ACEA B4 specification defines oils that are typically used in light commercial vehicles, such as the Mitsubishi diesel-powered Triton.

Meanwhile, Caltex is among major lubricant suppliers to develop a recipe for engine oils that meets standards for both gasoline- and diesel-powered passenger vehicles, said Sam Collyer, a spokesman for Caltex Australia, referring to the groups Havoline Synthetic range. This has come about thanks to reduced sulfur in diesel and a simplification of the diesel engine combined with a complication of the gasoline engine (direct injection and lean-burn technology) requiring oxidation stability and soot handling abilities.

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