In the pursuit of ultimate fuel economy Volkswagen has been ahead of the curve for a number of years. Its “1 Litre” concept car – named for the challenge of getting a production car to consume no more than 1 litre of fuel per 100km – was first shown to the public in 2002 and the XL1 is the final production realisation of that concept.
A few things have changed since the original prototype. The XL1 is still a two-seater, but uses a staggered side-by-side arrangement rather than the original tandem. This necessitates a pair of butterfly doors instead of the single canopy seen on the 1 Litre.
The components that power the car have also changed. The XL1 now uses a familiar plug-in hybrid system, comprised of an 800cc two-cylinder diesel producing 47hp and a 27hp electric motor. These drive a seven-speed DSG automatic gearbox and deliver power to the rear wheels.
More familiar though is the car’s construction. The XL1 uses composites extensively throughout the body, employing a carbon-fibre reinforced polymer (CFRP) monocoque. Where metal is absolutely necessary, Volkswagen uses aluminium (suspension, crash structure) or magnesium (wheels), while the brake discs are ceramic.
Keeping the weight down further, the side windows are polycarbonate and even the paint has been developed to be half as heavy as other CFRP paints. This all helps put the XL1’s weight at just 795kg despite carrying a diesel engine and batteries for a hybrid unit.
The design of the XL1 is specifically intended to disturb the air as little as possible. The coefficient of drag is 0.189, an almost unparalleled figure in production cars, while the car presents a cross section of just 1.5m2. The result of this is that to maintain 60mph on level ground, the XL1 uses just 8.3hp – compared to around 15hp for a conventional car.
All of this tech leads to a combined fuel economy of over 300mpg – 0.9l/100km – equivalent to 21g/km CO2. In full electric mode, the XL1 will travel up to 30 miles without any assistance from the diesel engine. With both engines working together, the XL1 can reach 60mph in 12.7s and continue to a limited top speed of 99mph.