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Diesel Cleans Up Its Act

The New Models are green, fuel-efficient and may be a better choice than a hybrid.

It's a spectacular summer day in Vermont, and I'm driving a new diesel SUV from Mercedes-Benz. Ironically, Vermont is one of a handful of northeastern states that follow California's rigorous vehicle-emissions standards, and diesel-vehicle sales have been banned here for years.

SLIDE SHOW: See the 2009 Diesel Models


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But now, Mercedes and a few other carmakers have diesel engines that meet those tougher standards, which require diesels to run as clean as gasoline engines. Mercedes has been selling its diesel models in 45 states, but as of August it began selling them in its most lucrative markets, California and New York, as well as Maine, Massachusetts and Vermont. (This year, Connecticut, Pennsylvania and Rhode Island are also adopting the California rules.)

What better place than Vermont to introduce diesels that can be sold in all 50 states? On the 100-mile drive through the Green Mountains, there's no trace of sooty exhaust to smudge the smog-free air. I get another surprise: The GL320 BlueTEC, Mercedes's large, seven-passenger SUV, gets 24 miles per gallon, which beats the Environmental Protection Agency number of 23 mpg on the highway. That's 6 mpg higher than the gasoline-powered V8 version of the GL.


The vehicle is quiet, and acceleration is fine, too, thanks to the torque-intensive engine. I could even tow a 7,500-pound boat or trailer. Mercedes-Benz is first out of the gate with nationwide diesels, but Volkswagen and BMW are also introducing 50-state models this year (see the box on page 96). Audi will follow with one early next year. By 2010, Honda, Nissan and the Detroit carmakers should also have diesels on the road. Mercedes is even planning to launch a couple of diesel-electric hybrid models next year.

Cleans Up Nice

Diesel technology has come a long way since Rudolph Diesel developed his engine in 1892. But among many Americans, diesel still gets a bad rap as a dirty technology. Even if you don't remember the clattering, soot-spewing, underpowered cars of the early '80s, you've certainly been assaulted by black smoke from diesel trucks and buses. Says Allen Schaeffer, executive director of the Diesel Technology Forum, an industry educational group: "There's clearly some stigma that the industry has to deal with -- is a diesel engine only for trucks? And do I have to go to a truck stop to refuel it?"

The answer to both questions is no. New-generation diesel cars are quiet and powerful, with turbocharged engines that overcome sluggishness at higher revolutions per minute. As for the availability of fuel, more than 40% of filling stations carry diesel. To see how many diesel-friendly stations are near you, use Mapquest's gas-price tool ( Clearly, there's no stigma about diesel in Europe, where more than half the cars sold have diesel engines.

And the newest diesels deserve a niche in the green-vehicle firmament. Diesel engines log up to 40% better fuel economy than comparably powered gas engines and emit about 20% less carbon dioxide, the primary greenhouse gas. The introduction of low-sulfur diesel fuel a couple of years ago set the stage for technology that could seriously clean up particulates -- that is, soot -- and reduce smog-forming nitrogen oxides.


So the fuel was available, but carmakers then had to meet strict new federal standards that took effect in January 2007. That turned out to be doable, but it took another 18 months for them to pass muster in California and the northeastern states that adhere to California's even-stricter emissions standards.

In a face-off between the 2008 Toyota Prius hybrid and the Volkswagen Polo BlueMotion -- a three-cylinder turbodiesel sold only in Europe -- the Polo looks every bit as green as the Prius. The Polo's 46-mpg fuel economy is about the same as the Prius's, but the VW emits less carbon dioxide. The Polo isn't coming to the U.S., but the Jetta diesel could be a Prius competitor.

It gets 29 mpg in the city and 40 mpg on the highway in EPA tests, and Volkswagen says that actual mileage is higher. Plus, diesel vehicles can run on biodiesel mixes made with vegetable oils or animal fats (or, with a few modifications, even fast-food vegetable fat). Currently, diesel engines can run on blends of up to 5% biodiesel, and carmakers are testing blends of 20% biodiesel.

Most of the antipollution technology is maintenance-free. But in Mercedes and BMW vehicles, nitrogen-oxide reduction requires treatment using urea. The onboard reservoir of urea, which the carmakers euphemistically call AdBlue, has to be periodically refilled at the dealership.


The Price Problem

You'll usually pay more for a diesel model, probably from $1,000 to $2,000 more than for the gasoline version of the same vehicle. That's mainly because the complicated antipollution apparatus is pricey. But the savings offset the extra cost. To start, clean-energy tax breaks, which are phasing out for some hybrids, will be available for the new diesels. The dollar-for-dollar tax credits can range from $400 to $2,400 in the year you purchase a diesel. For most passenger models, expect a credit of about $1,000.

Also, diesels are cheaper to own. Diesel engines tend to last longer than gas engines -- 200,000 miles or more. Diesel resale values are higher, too. And they're fuel-efficient. True, diesel fuel has been flirting with $5 a gallon. But the superior fuel economy of diesel engines means that you can pay as much as $5.20 per gallon and still break even with gasoline, assuming gas costs $4 a gallon and you get 30% better mileage with the diesel vehicle, which is a fair assumption. The price gap between gas and diesel fuel is unusually large right now and should narrow as refineries reduce gasoline production and increase diesel output.

Is a Diesel for You?

If you're in the market for a vehicle that gets good fuel economy, should you buy a diesel, a fuel-sipping gas-engine car or a hybrid? Or should you wait to buy a plug-in electric car?

A hybrid may be best if you do a lot of city driving and plan to own the vehicle long enough to offset the price premium with savings at the pump. But if you take a lot of long trips, a diesel is probably a better choice. With diesel, "you get the fuel economy and you get it all the time," says Schaeffer.


When the EPA recently revised the tests for fuel economy, diesel models logged slightly better results than under the old tests, while gas-powered cars got lower numbers.

And you may want to go with a diesel versus a hybrid given that hybrid technology is untested, relatively speaking. Questions remain about the longevity of batteries used to power current hybrids, and the lithiumion batteries for plug-in hybrids and electric cars are still in the development stage.

"Hybrids are still in their relative infancy, with the technology only about ten years old," Kevin Riddell, an auto analyst at J.D. Power and Associates, points out. Diesel's 115-year track record is one reason J.D. Power predicts that diesel vehicles (including pickup trucks) will own 8.1% of the automotive market by 2013, versus 6.9% for hybrids.

SLIDE SHOW: See the 2009 Diesel Models