Volkswagen’s carbon-fiber XL1 plug-in diesel hybrid is to be partially hand-built with initial production of reportedly only 50 units. It will be an uber-efficient machine possibly capable of cresting 300 mpg in certain situations, but trickle-down from it is already planned for the more pedestrian Up! city car.

Prices for the XL1 are not specifically known, could be in excess of six figures some have speculated, but its efficient 800cc, two-cylinder TDI plus 27-horsepower motor and 5.5-kwh battery pack can get the Up! up to serious mpg potential itself. The Up! would thus be made available for less money than will be demanded for the “most fuel-efficient production car in the world.”

Of course, prices are not known for the European market Up! plug-in hybrid either, given it’s still a work in progress, but Autocar says VW officials have pegged an 18-month window before launch for a car that could see 250 mpg or almost 1 liter/100km on the very lenient NEDC cycle.

Real world mpg could easily exceed 90 mpg for the little Up! plug-in hybrid which is an ideal candidate to have grafted in the semi-exotic XL1’s powertrain.

The Up! weighs just 2,039 pounds (925 kg), only 286 pounds (130 kg) more than the cost-is-no-object XL1. Its aerodynamics don’t come close to the XL1’s astonishing 0.189 cd, but being so light weight and small, it has a main part of the equation in place to become a more cost-effective runabout.

Power is transmitted through a 7-speed DSG gearbox and the vehicle could be capable of around 30 miles of all-electric driving on the modest capacity of its battery stored in the trunk area.

The hybrid system will offer a sail mode in which the clutch disengages the engine and the engine shuts off to further boost range where possible.
An electric motor reportedly restarts the system without a hiccup, by spinning the engine back to high speed while the car is on the go.

No doubt this beauty will not come inexpensive either, but has great potential, and will make a regular hybrid Toyota Prius c seem like a gas guzzler, assuming plans come to fruition in the next couple of years.