The world's most fuel-efficient car has just arrived on dealer lots in Germany and Austria, but don't expect it to be sold in America anytime soon.

The Volkswagen XL 1, a diesel-electric hybrid, gets about 260 miles per gallon—meaning, a New York-to-Washington run would guzzle just about a gallon of diesel. Chevrolet's all-electric Spark, America's fuel economy leader, gets half that many miles per gallon. The average U.S. car gets 36 mpg.

The XL 1's low carbon footprint is unrivaled among most car models—spewing 34 grams of carbon dioxide for each mile driven, compared to 10 times that from the typical U.S. car.

Although it's a limited production vehicle, the XL 1 is expected to boost technology development for super-efficient cars as regulations require automakers to address global warming. In April, the tiny two-seater was honored as a finalist in the 2014 World Green Car competition.

"The car offers a glimpse into the future," said Luke Tonachel, senior vehicles analyst at the Natural Resources Defense Council. Its "technology and innovation will work their way into mainstream vehicles."

Volkswagen is selling 250 models, which cost $150,000. About 50 have been sold.

The XL 1 is one of a handful of diesel-electric hybrid cars that have hit the European market in the last few years.

There are none, and no plans for any, in the United States, however, where even regular diesel cars haven't quite overcome their decades-old baggage of being dirty polluters. Less than five percent of U.S vehicles are diesel powered compared to about half of automobiles in Europe.

"The car was never designed for [the U.S.] market," said Volkswagen spokesman Mark Gillis. Its sideview mirrors, which were swapped out for cameras, and its single air bag don't comply with U.S. safety standards.

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The XL 1's fuel economy comes partly from its hybrid engine, and partly from its light and aerodynamic design. The car weighs 1,800 pounds, less than half the typical U.S. car. Its tires were slimmed down and its engine was shrunk and turbocharged to get more power. Even the body paint is extra thin. Like most hybrids, the XL 1 is particularly fuel efficient in stop-and-go or city driving, while its diesel engine excels on highways.

The fuel-efficiency modifications come with performance drawbacks and creature-comfort sacrifices. The air conditioner is weak, for example, and the diesel engine is noisy at low speeds. The car can't go above 99 mph and is slow to reach highway speeds.

Change Afoot in U.S.



Diesel engines are as much as a third more fuel efficient than gasoline ones and release minimal global warming gases.

But until recently they emitted dangerous levels of nitrogen oxides, a smog-causing gas, and small particulate matter. Strict air standards in America and Europe in the mid-2000s forced automakers to clean up their tailpipe emissions, and today diesel vehicles spew just slightly more smog pollution than their gas counterparts. But stateside, consumer interest has remained low. It hasn't helped that a gallon of diesel costs 40 cents more than gasoline. In Europe, diesel is cheaper than gas.

Change is afoot as automakers prepare for U.S. fuel economy standards, however, according to Allen Schaeffer, executive director of the Maryland-based Diesel Technology Forum. There are more than 40 different diesel models in the United States today, a dramatic increase in recent years. "For consumers, there are only going to be more choices," Schaeffer said. "We are definitely going to see the [diesel] market grow" to double, maybe triple its current size, he said.

The Obama administration's fuel economy standards are projected to require automakers to cut the global warming emissions of their average car in more than half by 2025, from 325 grams of CO2 emitted per mile to 144 grams per mile. Under the standards, an automaker's fleet must get about 55 mpg on average. Europe's emissions goal is for the average car to emit about 153 grams per mile of CO2 by 2021; its fuel efficiency goal is about 65 mpg.

Volkswagen has led the clean diesel transformation and dominates the diesel small car market in both Europe and North America.

The transportation sector accounts for nearly one-third of U.S. greenhouse gas emissions, and automobiles are the largest source.

Last month, California along with seven other states announced an action plan for how to put 3.3 million zero-emission vehicles—such as electric cars, hybrids and hydrogen-powered fuel cell cars—on the road by 2025.

There are about 161,000 electric vehicles and plug-in hybrids on U.S. roads today, comprising less than 1 percent of total cars.

