That is no small feat, but one the petite two-seater accomplishes with aplomb. The production version of a concept car that debuted at the 2011 Qatar motor show, the XL1 makes use of a plug-in hybrid powertrain comprised of a 27-horsepower electric motor and a turbocharged 2-cylinder diesel engine producing 47hp, which is matched to a 7-speed DSG dual-clutch gearbox. The bottom line: the XL1 returns a truly stellar 261mpg. To put that figure in perspective, that is New York to Washington DC on a single gallon of diesel fuel. Or Los Angeles to Las Vegas. Or London to Liverpool. It is impressive.

Drawing power from a lithium-ion battery pack, the XL1 can cruise for up to 32 miles on electric power alone. And although scintillating performance is hardly the XL1’s MO, performance is respectable: the 0-60mph sprint happens in 12.7 seconds and, with a determined (and patient) right foot, the speedometer needle will swing all the way to a limiter-governed 99mph.

Abetting its pursuit of maximum fuel economy, the XL1 wears seriously slippery bodywork. With a drag coefficient of just 0.19, it is the world’s most aerodynamic production car. (There is a nod to Honda’s original Insight coupe in its teardrop shape, no bad thing.) Total weight is a feathery 1,750lbs. Photos that have existed for more than two years do not do justice to the XL1. Here is a coupe that is low and tapered, with a sports car’s purposeful stance; its roofline is 5.1in lower than that of a Porsche Boxster. Like the Tesla Model S sedan, the XL1 offers compelling proof that environmental consciousness can be sexy.

The 2014 XL1’s launch will happen gradually. The company plans to deliver 50 hand-built cars to German drivers this year, likely through a special lease programme. In Geneva, the company was mum regarding plans for wider availability or a North American launch.