VW unveils an ultra-efficient car

Improved aerodynamics and weight reductions enable the car to use a smaller engine

Volkswagen has made a car it says can travel 313 miles on a gallon of diesel, and that emits just 24 grammes of carbon dioxide per kilometre travelled.

The XL1, which seats two adults, combines a 0.8 litre two cylinder diesel engine with an electric motor.

The car is constructed around a carbon fibre reinforced polymer monocoque to reduce the weight to just 795 kilos.

German rival BMW is also making an electric carbon fibre car, while Mercedes is to make carbon fibre parts.

Their efforts show how the motor industry is increasingly working to improve aerodynamics and reduce weight, in order to supplement improvements in cars' engines.

On the engine front, electrification is becoming mainstream even though pure electric cars are expected to remain niche products for decades yet.

Instead, carmakers are increasingly combining conventional solutions, such as petrol or diesel engines, with battery-powered solutions.

"All sorts of mixes will come to the fore," said Jim O'Donnell, BMW North America's chief executive, in an interview with BBC News.

The Volkswagen XL1 is to be formally unveiled at the Qatar motor show on Tuesday night.

The carmaker says it can accelerate from nought to 100 kilometres per hour (60 miles per hour) in 11.9 seconds.