BMW is reportedly developing an ultra-fuel efficient car that consumes just 0.4 L/100km (588 mpg US / 706.2 mpg UK).

According to Automobilwoche's sources, the car is four-seater that has a carbon fiber reinforced plastic body and an extremely low drag coefficient.  The model is also rumored to weigh less than 1200 kg (2645 lbs).

The car's powertrain remains shrouded in secrecy but the model is reportedly a range-extended electric vehicle which uses an electric motor and a two-cylinder petrol engine that acts as a generator.  While the model will likely be slow, it will reportedly have a top speed of at least 180 km/h (111.8 mph).

While Volkswagen eventually put the XL1 into production, the chances of seeing a production version of BMW's eco-friendly model remains "questionable."

Gallery: BMW is reportedly developing an ultra-fuel efficient model that returns 588 mpg

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