Diesel On the Road to Improvement, but Gasoline and Hybrids Still Cleaner

Improved diesels would be 2.5 times more expensive than gasoline for a 30% improvement in fuel efficiency, report says.

Published: 07-Jan-2004

A new report from the Union of Concerned Scientists finds that diesel cars of the future can be much cleaner than today's diesels using pollution controls under development and can provide consumers with cost-effective fuel economy gains. However, the study also finds that improved gasoline vehicles and gasoline-electric hybrids will likely remain cleaner than diesel and can save consumers more money for similar reductions in oil and heat-trapping gas emissions. The study comes as automakers and their political allies promote diesels as a means to address concerns over oil dependence and global warming.

"New pollution controls may one day clean up diesel's dirty image," said Patricia Monahan, a senior analyst in UCS's Clean Vehicles Program and lead author of The Diesel Dilemma: Diesel's Role in the Race for Clean Cars. "But, head to head, our report shows that improved gasoline vehicles are the better buy."

The new UCS study uses detailed modeling to examine for the first time how diesel and gasoline vehicles compete among a variety of cars and trucks, applying improved engines and other conventional fuel-saving technologies that could be implemented today, as well as advanced and hybrid technologies that could be implemented within the next 10 to 15 years.

According to the report, improved diesel and gasoline vehicles could reduce oil use, compared with today's vehicles, by as much as 40 percent using conventional technology. Hybrid-electrics could cut oil use by as much as 50 percent. However, for similar reductions, the sticker price of diesels would be much higher than improved gasoline and hybrid gas-electric vehicles. For example, it would cost a consumer about $2,800 over the price of today's vehicle for an improved diesel that could cut oil use by about 30 percent -- greater than 2.5 times more than it would cost to achieve the same reductions with an improved gasoline vehicle.

The higher costs of both improved diesel and gasoline vehicles are more than offset by reductions in fuel costs, on balance saving consumers between $400 and nearly $2,000 over a vehicle's useful life, depending on the technology package. But in all cases the report finds that improved gasoline vehicles save consumers more money because of their substantially lower initial price tag.

"Proponents should not oversell diesel technology as a silver bullet," said David Friedman, research director for UCS's Clean Vehicles Program and a co-author of the new report. "While diesels may eventually shed their image as an industry black sheep, they still can't match the pollution performance of today's cleanest gasoline cars."

Diesel vehicles appear to be on track to meet the weakest, and possibly the average, federal emissions standards coming into full effect in 2009. But the structure of these standards will allow some cars to release two times more soot and nearly three times more nitrogen oxides than the average new vehicle in government tests. Further, today's standards do not address concerns over much higher emissions in real-world driving and mounting evidence that unregulated pollutants may pose significant health problems.

"The United States must not follow Europe's lead when it comes to diesel policy," said Friedman. "Diesels should just be allowed to compete equally in a market that protects public health and the environment -- they certainly don't deserve emissions loopholes and unfair tax breaks."

New car buyers considering diesels should -- at a minimum -- look for a vehicle certified to the average federal Tier 2 standard (known as Bin 5) and should let their dealer know they also want clean and efficient gasoline options. Since low-sulfur diesel fuel is made with more oil than reformulated gasoline, consumers should also discount a diesel vehicle's fuel economy by about 20 percent to evaluate the amount of oil used relative to a gasoline vehicle. For more information about The Diesel Dilemma: Diesel's Role in the Race for Clean Cars, visit UCS on the web at www.ucsusa.org.

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