Here's the breakdown, Volkswagen made a hybrid car that is the most economical car, which runs on a diesel engine and an electric motor. Plugging it into a regular electric outlet at home can also charge the lithium ion battery. The body is made out of carbon fiber-reinforced polymer parts to lower drag. See Here
Volkswagen says the XL1 hybrid consumes 0.9 liters per 100 km (313 mpg) and its CO2 emissions are 24 g/km. It can accelerate from 0 to 100 km/h (62 mph) in 11.9 seconds, and its top speed is electronically limited to 160 km/h (99 mph).
Let's just assume that these stats are completely accurate, if they are then this probably is the world's most economical car. The demand for oil will definitely decrease in the UK and Germany seeing as the release of the car is in those two countries by 2013. 313 miles per gallon is absolutely ridiculous, but that's only if you charge the car at night or whenever. Just a few downsides to point out here, the rear tires seem like a complete hassle to change along with getting snow or ice out of them. This car probably takes up a ridiculous amount of electricity if it gets 313 miles per gallon. If one is fine with paying for a higher electric bill and being more nature friendly than paying for gas, then by all means roll with it. At least the car will make a large enough impact in the UK or Germany in demand for gas that the suppliers will send more to the U.S.