MICHELE NORRIS, host:
For decades, diesel vehicles have had a lousy reputation for being noisy, smelly and polluting. Their one saving grace was that they went farther on a gallon of fuel.
NPR's Elizabeth Shogren reports that diesel has cleaned up its act and automakers are now pitching diesel cars as green vehicles of the future.
ELIZABETH SHOGREN: Outside the Washington, D.C., auto show, Volkswagen's Marijke Smith is idling in a shiny blue sedan.
Ms. MARIJKE SMITH (Public Affairs Manager, Volkswagen of America, Inc.): This is a 2009 prototype Volkswagen Jetta, diesel.
SHOGREN: It's not noisy, and there's no plume of black smoke coming out of the tailpipe. The car won't be available until late summer, so there aren't any official mileage estimates yet, but Smith says it will give most hybrids a run for their money.
Ms. SMITH: What we're estimating is that it will probably be in the high 30s/low 40s in the city and high 40s/low 50s on the highway.
SHOGREN: The new diesel Jetta is supposed to be clean enough that it will be available even in California, where tough smog standards have kept new diesels off the market for many years.
Inside the auto show, there are more diesels on display probably than ever before. BMW has one, so does Mercedes.
Mr. ALLEN SCHAEFFER (Executive Director, Diesel Technology Forum): And there's going to be more coming to this diesel party.
SHOGREN: Allen Schaeffer represents the Diesel Technology Forum, a trade group that promotes cleaner diesel.
Mr. SCHAEFFER: Toyota announced that they will be bringing a diesel engine into their full-size SUV, the Sequoia and the Toyota Tundra pickup truck. And Hyundai is going to have the Veracruz in a diesel in two years, as well.
SHOGREN: Schaeffer says a few factors have contributed to diesel's rise. One is that the government adopted new fuel economy standards, and diesel cars go farther on a gallon of fuel than gasoline cars. Another is that government mandates have cleaned up diesel — both the fuel and the cars themselves. A third is that most diesel cars emit less greenhouse gases, which addresses growing concerns about climate change.
None of these is news to Sarah Myers and her mother, Sue Ellen. They arrived at the car show with a mission.
Ms. SARAH MYERS: We came to look at the new clean-burning diesel Jeep that's coming out.
SHOGREN: Sarah runs a free-trade import company and uses her aging Jeep to pull a trailer. Her mother uses hers on her family farm. Both women are waiting for a new diesel Grand Cherokee that's supposed to be really green.
Ms. MYERS: That's the one downfall that we've always had with the Jeeps. I don't feel so bad about it because I use it in ways that I couldn't use like a Civic hybrid or the Prius, but I hate the high gas mileage, so the diesel makes me feel a lot better about driving a Jeep.
SHOGREN: As it turns out, Jeep wasn't showing the SUV they hope to buy. In fact, a Jeep spokesman says it won't be available for another couple of years.
Jeep already sells another diesel Grand Cherokee. But it pollutes more than the one on the drawing board. And the federal government says its greenhouse gas footprint is slightly bigger than the gasoline version.
David Friedman, from the environmental group Union of Concerned Scientists, says it helps illustrate one of the caveats to diesel's environmental credentials.
Mr. DAVID FRIEDMAN (Union of Concerned Scientists): Because you use less fuel, you tend to produce less global-warming pollution, but of course with diesel there's a bit of a catch.
SHOGREN: And the catch is that even though diesels go farther on a gallon of fuel, diesel fuel is higher in carbon. So, per gallon, diesel engines emit more carbon dioxide, a major greenhouse gas. Also, it takes more oil to make a gallon of diesel than a gallon of gasoline, and refining diesel creates more air pollution. Still, most diesel engines should send 10 percent to 20 percent less greenhouse-gas pollution into the air than similar gasoline engines.
Friedman says this shows why today's consumers need to be more careful shoppers.
Mr. FRIEDMAN: You need to do things like go to fueleconomy.gov and do your research and compare not only the fuel economy of the vehicle, but also how many barrels of oil is it going to use, how much global-warming pollution is it going to produce. You've got to do your homework.
SHOGREN: Diesels face a bigger challenge: their image.
Pam Loeb was looking at a new diesel at the auto show, but she says she'd never buy one.
Ms. PAM LOEB: I've never been much of a fan. They were low powered, and they didn't smell very good, so not for me.
SHOGREN: Several car companies see that bias as too high of a hurdle. They're investing in hybrids instead. Some say they'll only try diesels in large SUVs and pickups. But some automakers, like Volkswagen, are betting that the new, cleaner diesels will take off.
Elizabeth Shogren, NPR News, Washington.
NORRIS: And you can see how two of these new diesels compare to conventional cars at our Web site, npr.org.