From
www.wisegeek.com:
Europe also uses more diesel power than the United States does: of the top ten fuel-efficient cars in Europe, only one uses conventional gasoline.
The most fuel-efficient cars in Europe all have fuel efficiency over 64 miles to the gallon, which translates to 27 kilometers per liter. The car which tops the list is the Citroen C1, followed by the Toyota Aygo, Renault Clio, Citroen C2, Fiat New Panda, Toyota Prius gasoline hybrid, Citroen C3, Vauxhall Corsa, Peugeot 206, and another model of the Vauxhall Corsa. Many of these cars are available in other parts of the world including Africa and Asia, where a high premium is placed on gas efficiency as well.