Justin Timberlake presents the Audi A1 at the Geneva Motor Show in Switzerland in 2010. Timberlake stars in a viral marketing campaign for the car company aimed at a younger demographic. Audi's share of the luxury market has risen in recent years. Martin Meissner/AP hide caption

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Professor Anna Stefanopoulou (left) examines a V8 internal combustion engine with students Jacob Larimore and Xinfan Lin at the University of Michigan's Automotive Research Center. The researchers model engine performance to improve efficiency. Courtesy Automotive Research Center hide caption

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Attendees at the Los Angeles Auto Show look at the BMW i8 plug-in hybrid concept car. Toyota's Prius is the best-selling hybrid on the market, but almost every carmaker has some form of hybrid technology. Jae C. Hong/AP hide caption

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A Nissan Leaf charges at a station in Portland, Ore., that can recharge an electric car in 30 minutes. Electric cars could be an integral part of meeting 55-mpg fuel standards by 2025, but many consumers are put off by the vehicles' higher price and what some call "range anxiety." Rick Bowmer/AP hide caption

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Workers put together a Ford Explorer on the assembly line at the automaker's Chicago plant in 2010.

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The new redesigned 2012 Toyota Camry is unveiled during a news event on the Paramount Studios lot in Hollywood, Calif.

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A Hyundai Genesis Coupe is on display in a showroom in Glendale, Calif., last January.

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