Since first being introduced in 2002, the Volkswagen L1 Concept has been dubbed the most fuel efficient automobile in the world. While this is a lofty claim on the part of VW, the evidence to support this title seems to be sufficient.
The L1 is named for the 1.38 liters of diesel fuel it consumes per 100 miles of travel. Yeah, it is a little misleading, but calling it the L1.38 wouldn't roll off the tongue nearly as nicely. This exceptionally low number comes from the use of a 0.8 liter TDI powerplant connected to a 10kW electric motor. When wound all the way out, the L1 concept is capable of reaching 100mph.
The L1 is capable of operating in two different modes. The first and most fuel efficient is the "Eco" mode, which will likely use the diesel engine to produce energy for the electric motor. The other is a "Sport" mode, which will use the diesel engine and electric motor simultaneously.
The exterior was meticulously studied to keep drag to a minimum, with the final number being a mere 0.195 drag coefficient. All tallied, the current estimate from VW is placing the L1 Concept at 170mpg. Even more interesting is the 2013 production date announced by the German Automaker. It is unsure if this timeframe is official.Engadget