The automaker says pioneering construction techniques, an advanced plug-in hybrid drivetrain and innovative packaging all play a part in allowing the XL1 to return 313mpg (in non-metric terms) on the combined cycle while emitting a mere 24g/km of CO2 - to benchmark for vehicle efficiency.
Powering the XL1 is a compact two-cylnder, 800cc TDI common-rail 36kW diesel engine. It’s linked to 21kW electric motor but their power combined, VW says, is more than enough for a car that weighs only 795kg.
Both power units are linked to a seven-speed DSG gearbox with an automatic clutch mounted between the units. The electric motor can work alone or in tandem for acceleration. The XL1 can travel 35km on battery power, at which point the the diesel engine will fire up.
Acceleration to 100km/h takes 11.9sec, top speed is electronically limited to a shade less than 160km/h.
SLIPPERY CUSTOMER: The XL1's styling allows easy access through scissors doors and its wind tunnel-proved profile has a drag co-efficient of an amazing 0.186.
To make such weight savings possible but viable for series production, VW says it developed and patented a new system for the manufacture of the carbon fibre-reinforced polymer parts of the car and called it "resin transfer moulding".
The balance of the car's weight is made up of its drivetrain (227kg), running gear (153kg), interior including a pair of bucket seats (80kg) and the electrical system (105kg). Only 23% of the car (184kg) is steel or iron.
More weight was shed through the extensive use of light materials such as magnesium (wheels), ceramics (brake discs) and aluminium (shock-absorbers, steering system, brake callipers).
MAKING LIGHT OF IT: Everything in the XL1 has been calculated to save fuel - even the weight of the bucket seats.
Although the XL1 is still very much a concept, VW says, its unveiling is the next step towards the creation of a new class of Super Efficient Vehicles "while the advent of a process such as RTM is a significant milestone".