It's the BMW Vision, a car that has an ultra-efficient turbo-diesel engine and two electric motors that could combine to make it the greenest sports car that isn't a Tesla Roadster. Of course the 400 mile range (not to mention the backseat) makes the Vision a tad more practical.
BMW will be officially unveiling the car at the Frankfurt Motor Show in a couple of weeks, but we're getting a HD preview in the form of the following video.
The car doesn't just get an EcoGeek's approval because of the plug-in system, which can carry the vehicle for 30 miles on a 2.5 hour charge. The 1.5 liter turbo-diesel engine is also extra green, and its placement over the rear axle allows for an extremely low front-end, which decreases drag significantly. Additionally, the concept has been created using extremely light-weight materials and a battery chemistry that allows for less battery weight. Of course, the lighter a car is, the less fuel it has to use.
While the car can drive on electric power alone, it isn't an extended-range electric vehicle like the Volt. The turbo-diesel can re-charge the battery, but it can also be used to power the wheels. The idea is that, if you really want to pull out all of the stops, the diesel engine can kick in and work with the electric engines, thus making the car "perform like a BMW."