There are three main ways to improve fuel efficiency. You can decrease the power output of the engine, drop significant weight from the vehicle, or make the car work more efficiently, getting the most power out of every drop of petrol.  I'm not sure about the last of the three, but Volkswagen definitely has the first two of those ideas down pat with their latest prototype, a four-wheeling car that uses less than a litre of gas per 100 kilometres traveled (about 240 miles per gallon!).

The conceptual necessity for a small frontal area led to an unusually narrow and very flat body form being chosen. The body was developed in a wind tunnel, is 3.47 metres long, but just 1.25 metres wide and just over a metre in height, and is made completely of carbon fibre composites. To save weight, it is of course not painted. The carbon-fibre-reinforced outer skin is tensioned over a spaceframe that is not made of aluminium, but rather of magnesium, which is even lighter.

The 1-litre car is powered by a one-cylinder diesel engine, centrally positioned in front of the rear axle and combined with an automated direct shift gearbox. The crankcase and cylinder head of the 0.3-litre engine are of an aluminium monobloc construction. The naturally aspirated, direct-injection diesel engine employs advanced high-pressure unit injection technology to generate 6.3 kW (8.5 bhp) at 4,000 rpm. This gives the vehicle, which weights just 290 kg, an astonishingly lively temperament. Fuel consumption is a mere 0.99 litre per 100 kilometres. With a 6.5-litre tank, this gives a range of some 650 kilometres without refuelling.

Due to the restriction of space, it was not possible to adapt an existing gearbox. For this reason, a compact, automated 6-speed gearbox is employed, which is controlled from a turn switch in the cockpit. Running gear made of lightweight alloy, tyres that offer optimised rolling resistance and 16-inch wheels made of extremely lightweight composite material perfectly complement the economical drive system.

Don't expect to see anything like this in showrooms any time soon, but it is a good indication as to where the automotive industry is heading.

In related news, VW launches new "Crash" shock ads - the 30-second spots depict friends riding in the new Jetta and then being involved in a serious accident. Thanks to the car's safety features, they are OK. Will these ads help sell Jettas? Have a look after the jump...