Volkswagen has been on a quest this decade to develop a car capable of going 100 kilometers (62.5 miles) on less than 1 liter (a hair over a quart) of fuel. The XL1, revealed at the Quatar auto show this week, is the third proof-of-concept car in that effort. Volkswagen says it plans to produce and sell a car based on the XL1 in about two years.
Despite its name, the XL1 is anything but extra large. It is a tiny two-seater that is a little shorter than a Honda CR-Z and a lot lower. Unlike the previous two concepts (the 1-liter and the L1), the XL1 at least moves to traditional side-by-side seating, rather than a tandem (fore and aft) configuration. Nevertheless, it has a drag coefficient of just 0.18. (For comparison, the slipperiest mainstream production car, the 2011 Toyota Prius has a Cd of 0.25, and a Chevrolet Corvette Z06 cuts the air with a 0.34 Cd.)
Plug-in hybrid technology and a diesel engine give the XL1 fuel consumption of just 0.9 liters per 100 km, or the equivalent of 261 mpg, VW says. The electric part of the drivetrain can carry the XL1 up to 35 miles using lithium-ion batteries and a 20 kw electric motor. After that, a 48-hp, 800-cc two-cylinder turbodiesel engine (basically half of a smaller version of VW's TDI) comes on to give the car a 341-mile range. The engine and motor are connected ahead of a seven-speed dual-clutch transmission driving the rear wheels. (See our VW Golf TDI road test.)
Since VW is not stating battery capacity, the mpg number presumably doesn't count the electric power consumed.
The XL1 demonstrates how far relatively conventional technology take fuel economy. It will be interesting to see if Volkswagen is able to bring this car to market overseas and how successfully they can bring down the cost of producing the carbon-fiber body.
See our guide to fuel economy for advice on saving gasoline. Learn about future technologies in our guide to alternative fuels.