Qatar

With fuel-efficiency and emissions regulations tightening all over the world, carmakers continue to push the limits on how economical a production car can get. The latest entrant in the high-mileage stakes: a future edition of Volkswagen's Up minicar that will return 79 miles per gallon using a two-cylinder diesel engine paired with a hybrid system using a lithium-ion battery pack. If that sounds vaguely familiar, it's because it's the same powertrain that Volkswagen intends to use in its limited-production, high-tech XL1 two-seater. That car, the third iteration of a decade-long Volkswagen...