At the Frankfurt Motor Show, Volkswagen debuted its ultra-efficient L1 Concept, which serves as a followup to the One-Liter Concept from 2002. Like the One-Liter, the L1 derives its name from the fact it takes around one liter of fuel to propel the car 100 kilometers (62 miles).

As it turns out, the L1 might not quite live up to the One-Liter's impressive 235 mpg rating. The car is said to consume closer to 1.38 liters of gas to travel 100 km, so that work out to 170 mpg, which is, of course, still very impressive.

Of course, there's a trade-off for all that efficiency. The L1 is extremely lightweight at 1,100 lbs, and it has space for just two occupants. The passenger sits behind the driver, and storage is limited.

Power comes from a 36-horsepower two-liter diesel motor coupled to a seven-speed dual-clutch gearbox.

Rumor has it a production derivative could arrive in 2013. Further details on the car have not been disclosed.