11 mileage-obsessed questions

The 2009 VW Jetta diesel gets 41 mpg on the highway.

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A. Popular in Europe, diesel is 20% to 40% more efficient than gas. And now a diesel car won't make your garage smell like a truck stop: The fuel itself contains far less sulfur than it once did. Plus, diesel cars today have more efficient engines, and most 2009s will pass the same emissions standards as gas vehicles.

The compliant 2009 Volkswagen Jetta diesel - which gets 41 mpg on the highway - went on sale in August; Audi, Honda and Mercedes-Benz will follow with models in the next few months.

But experts predict that the U .S. will be slow to adopt these vehicles: Diesel is sometimes pricier than gas here, reducing or even negating potential savings. (In August 2007 diesel cost about the same as gas; recently it was $4.71 when gas was $3.93.) In the Northeast and Midwest, where houses are heated with oil similar to diesel, the cost goes up in winter.

Also, you'll pay a minimum $1,000 premium on these cars. To see if diesel would make sense for you, use the "Side-by-Side Comparison" tool at fueleconomy.gov, entering in local gas and diesel prices.

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