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Diesels: Better Mileage, More Power

Diesels: Better Mileage, More Power

By Jeff Youngs, February 24, 2012
There have been many developments and substantial improvements in diesel technology since the 1980s. (Interestingly, diesel engines first appeared in the U.S. automotive market in the mid-1930s.) Today's diesel engines yield higher fuel economy and provide better performance than their gasoline counterparts. They provide 20 to 40 percent better fuel economy and offer more torque at lower rpm compared to gas engines. Diesel engines are also substantially less harmful to the environment today than they were in the past, and they will become even cleaner in the near future.

Why aren't diesel-powered vehicles more popular in the United States? First, diesel-powered vehicles are usually more expensive than their gasoline counterparts. Secondly, diesels don't meet emissions standards for all 50 states, including some states (such as California) that annually have a large number of new-vehicle sales. On the plus side, in July 2005, Congress passed legislation that will give buyers of clean diesel vehicles tax credits of up to $3,400 per vehicle, an incentive designed to offset the increased cost of diesel technology. This is the same reasoning used to provide tax credits to buyers of hybrid vehicles.

Renewed American interest in diesels

Interest among U.S. consumers in diesel-powered vehicles is on the rise, thanks to the increased power and improvements in fuel economy that diesels provide. According to J.D. Power and Associates, the number of diesel-powered vehicles purchased by U.S. consumers will more than double by 2012. (Source: J.D. Power Automotive Forecasting,SM 4/13/2006)

Many U.S. consumers are already purchasing light-duty diesel-powered vehicles, which are not available in all states. Currently, no light-duty diesel-powered vehicles are sold in California, Maine, Massachusetts, New York, or Vermont due to stricter emissions regulations in those states. (Diesel-powered trucks, however, such as heavy-duty versions of the Chevy Silverado, Dodge Ram, and Ford F-Series, fall under different emissions regulations and are available for sale in all 50 states.)

New standards for 2007

While current emissions standards are different for diesel engines and gasoline engines, new federal standards that go into effect in 2007 require diesel-powered vehicles and gasoline-powered models to meet the same emission standards. In some respects, such as carbon-dioxide emissions, diesels are actually more environmentally friendly than gasoline engines, but pollutants such as nitrogen oxide and soot present a different set of challenges. On average, the new standards will result in a 77 percent reduction in nitrogen-oxide emissions and an 88 percent drop in particulate emissions.

The big challenge is that modern-day emissions control systems, which filter out nitrogen oxides and particulates, don't work well with today's U.S. diesel fuel, because it has a much higher sulfur content than diesel fuel sold in Europe. The EPA has mandated that diesel fuel be produced with a lower sulfur content beginning in 2007, but even reduced sulfur content isn't enough to make U.S. diesel fuels as clean as those in Europe.

Much work is being done today to develop systems that reduce emissions from diesel engines to a level that will meet future U.S. standards. One possibility is a system that would require the owner to add a powdered substance to the vehicle's fuel system regularly, akin to adding windshield washer fluid. There is a concern, however, that owners won't add it because there will be no noticeable difference in the vehicle performance without it-the vehicle simply won't be emissions compliant. Another option is to use a component that would trap the particulate matter before it is expelled through the tailpipe, but these systems need to remain clean in order to be effective.

As with hybrids, diesels are making slow, but steady, inroads in the U.S. automotive market. Ultimately, their success will depend on mainstream market acceptance of the technology as well as the commitment from the automakers to continue developing, producing, and selling these vehicles.
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