The vast resources of the Volkswagen Group have yielded some rather impressive vehicles, and you might think that its sixteen-cylinder beasts like the Bugatti Chiron and Veyron are foremost among them. We're not here to argue that point, but if there's anything the German giant has ever developed that's even more impressive, it's the Volkswagen XL1. And there just so happens to be one up for sale right now.

Never heard of the XL1? Allow us to bring you up to speed – slowly, quietly, and with but a thimble full of petroleum.

Also known as the "one-liter car," the Volkswagen XL1 was made to show just how far it could stretch our notions of an economical mode of transportation. The plug-in hybrid featured a wind-cheating shape with a ludicrously low drag coefficient of less than 0.19 – less than a Tesla, a Prius, or just about any other production road car (save, perhaps, for the GM EV1).

That was part of the equation. The other was its highly efficient powertrain. Developed before the Dieselgate scandal hit, the XL1 packed an 800cc two-cylinder turbodiesel engine good for just 47 horsepower, coupled to a 27-hp electric motor and a seven-speed dual-clutch transmission.

With so little power to play with, it took nearly 12 seconds to reach highway speeds, and despite its slippery form, it couldn't even reach 100 mph. But that wasn't the point. The point was that it could travel for around 300 miles before needing to plug in or fuel up, could go for 50 kilometers (31 miles) on electric power alone, and only needed a liter of diesel to travel a hundred kilometers (or 62 miles) – hence its moniker. Impressive as it was, though, the XL1 wasn't as cheap to buy as it was to run.

Only 250 of them were made, each retailing for €111,000 (or about $123k at today's rates). This particular 2015 model has just 300 miles on it, which means its owner barely ever saw just how far it could go on so little. And that could be why it's still demanding such a high price: Heritage Automotive in the southwestern English town of Salisbury has it listed for £79,950 (or about $104k) – which wouldn't be enough to get you a Bugatti but would be just enough to put you behind the wheel of a new Porsche Taycan.