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NEW YORK (CNN/Money) - When car shoppers look for really high gas mileage, they usually think about hybrids, which run on a computer-controlled combination of a regular internal combustion engine and one or more electric motors.
But there's another way to get great mileage: a diesel engine.
While Toyota and Honda have become well-known for their hybrids, Volkswagen is less acclaimed for its own high-mileage cars, like the diesel-powered New Beetle TDI. It gets an EPA-estimated 38 miles per gallon in the city and 46 miles per gallon on the highway.
Volkswagen also sells several other diesel-powered cars in the United States.
Those mileage numbers aren't quite up there with the most efficient hybrid cars, but they also don't come with all the complexity of hybrids.
Mercedes also sells a diesel car in the United States now, the E320 CDI. The Jeep division of DaimlerChrysler offers a diesel version of its Liberty SUV, as well.
While diesel-powered passenger cars are common in Europe, they haven't caught on here.
That's partly because the diesels most U.S. drivers are familiar with are the noisy smelly trucks and buses they get stuck behind in traffic. Or they may remember the diesels their neighbors bought during the last big fuel economy crisis in the 1970s.
Either way, diesel has become associated with noisy clatter, puffs of black smoke and patience-testing acceleration.
Modern diesel engines are considerably better than that. No black smoke, fewer rattles and acceleration that's at least on par with gasoline-powered cars.
While diesel cars get about 30 percent better mileage, overall, than comparable gasoline-powered cars, they are most efficient in steady highway driving, said David Champion, head of auto testing for Consumer Reports.
Hybrid cars, on the other hand, are most efficient in city or suburban driving, which calls for frequent acceleration and braking.
In terms of performance, modern turbodiesel-powered cars -- all diesel engines in today's passenger vehicles are turbocharged -- provide a driving experience that is no different from a gasoline engine, Champion said. In fact, passing power is greater than with a gasoline engine.
When pressed to accelerate from 50 to 70 miles per hour, a diesel car "takes off like nothing on Earth," said Champion.
There are some downsides. For one thing, diesel engines require more expensive oil changes using high-performance synthetic oil, Champion said.
And while diesel gasoline pumps are more common at gas stations today than they once were, filling up with diesel is a less tidy experience than many car owners are used to.
Diesel pumps are usually placed far away from the main "island" of gas pumps and they aren't as clean and nicely maintained. That's particularly a problem because of the strong smell of diesel fuel, which won't come off easily once it's on your hands or shoes.
"Diesel fuel stinks compared to gasoline," said Champion.
The main difference between gasoline and diesel engines is that gas engines use a precisely timed spark plug to ignite a mixture of gasoline and air that has been compressed by a moving piston inside a cylinder.
In a diesel engine, air, warmed by a heating element, is compressed inside a cylinder until a precisely timed spray of fuel is pumped in. The fuel is immediately ignited by the hot, compressed air, pushing the cylinder back down.
The high compression of diesel engines means the engines have to be built stronger. As a result, diesel engines typically last longer than gasoline-powered engines.
Because of those longer-lasting engines, diesel vehicles often retain considerably more of their value over the years than similar gasoline-engined cars. That extra savings, combined with better fuel efficiency, should more than make up for any added maintenance costs.
Diesels typically cost about $2,000 more than a similar gasoline-powered car. The added cost to the consumer of a hybrid powertrain is difficult to judge because manufacturers usually add other unrelated features to their hybrid models, but it has been estimated at about $4,000
Gas savings aside, diesels are not as kind to the environment as hybrids. Diesel engines still produce more pollution than gasoline engines.
Cleaner diesel fuel, which the government has mandated must be available at pumps starting in the autumn of 2006, will help with these problems. The new fuel will contain much less sulfur than it currently does.
The presence of sulfur in diesel fuel interferes with technologies that could clean diesel emissions. With most of the sulfur removed, carmakers say, it will be easier to clean up diesel exhaust.
"Low-sulfur fuels are absolutely critical to us having a successful diesel market in the U.S.," said Max Gates, a spokesman for Chrysler, which currently sells the diesel Jeep Liberty.
Low-sulfur fuels will also be critical to meeting stricter federal emissions guidelines for diesels and all passenger vehicles. Those guidelines will phase in along with the cleaner fuel.
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