That a diesel car and a diesel truck were among the finalists this year for car and truck of the year as part of Detroit's North American International Auto Show underscores the positive role diesels can play in conserving oil. In some ways, diesels are a forgotten solution for decreasing fuel consumption.

The diesel entries were the 2009 Volkswagen Jetta TDI car and Mercedes-Benz ML320 BlueTEC crossover truck.

Diesel vehicles enjoy significantly greater fuel efficiency than their standard gasoline counterparts. Typically, that advantage amounts to about 30 percent.

The U.S. Environmental Protection Agency estimates annual fuel costs for the diesel Jetta at $1,800. Detroit News auto reviewer Scott Burgess notes this is about $500 less than the cost of driving the best standard gasoline Jetta model.

The EPA has estimated that if one-third of the light vehicles on the American road were diesels, the United States would need about 1.4 billion fewer barrels of oil a day.

Burgess, in a review of the Jetta TDI last month, estimated that the car's average fuel efficiency in his commute from his home to The News, which included both city and highway driving, amounted to 39.6 miles per gallon.

In the past, diesel passenger vehicles were noted for their rough rides and strong soot emissions. But the Jetta meets current U.S. emissions standards and rides well. Other manufacturers, including BMW, are preparing to tout cleaner diesels that run on lower-sulfur diesel fuel.

The major drawback to diesel cars is that diesel fuel costs more than standard gasoline. But based on their greater mileage, diesel vehicles are eligible for federal tax credits.

Diesels aren't the only solution to reducing fuel consumption. Gasoline-electric hybrids will also play a role. But the technology for producing diesel engines is well developed. More than half of the cars in Europe are powered by diesel fuel, not least because such fuel enjoys a tax advantage.

And because diesel fuel already plays such a major role in powering commercial vehicles such as large trucks, buses, tractors and construction implements, the infrastructure exists to make it widely and easily available to autos.

Hybrids and a coming generation of plug-in vehicles that can meet the needs of the average family, by contrast, will require the development of special batteries and charging stations.

It should be the policy of the incoming Obama administration to encourage all technologies that reduce oil consumption. This should include diesel technology. By contrast, California's regulations discriminate against diesel vehicles, says Jim Hossack, vice president and senior consultant in the Southfield office of AutoPacific, an auto consultancy.

Emissions standards shouldn't be ratcheted up any further — and producers of vehicle technology shouldn't be required to meet more than one national standard.

Consumers can then choose which vehicle technology best meets their individual needs.

REPRINTED FROM THE DETROIT NEWS.