Rival luxury carmakers are pursuing different strategies to reduce vehicle weight to combat the increased kilograms new cars gain from additional safety and comfort features.

Jaguar is fully committing itself to aluminium while Audi takes a more conservative approach to using the material.

Jaguar plans to use aluminium in all its segments with the possible exception of the next X-type while Audi will use the material in two of its six models, industry sources told Automotive News Europe.

Carmakers primarily use aluminium for luxury models to improve fuel efficiency because it is lighter than conventional steel. The material is seen as a crucial part of the car manufacturers' quest to reduce CO2 emissions to 140 grams per kilometre by 2008 from the current 165 g/km.

A downside is that aluminium is more expensive to make and work with than steel.

Audi also will continue to build its all-aluminium A8. But poor sales of the all-aluminium A2 have stung Audi, so it will stop producing the car in 2005.

Industry sources say the A2 is about €400 more expensive to build than a steel version.

Jaguar will have aluminium models across the board. The only possible exception is the X-type, if a new generation of the model is built.

The current XJ series features an aluminium unibody. At just 1539 kilograms it is by far the lightest vehicle in the upper luxury segment. In comparison, the all-aluminium Audi A8 weighs 1,670kg. Steel-bodied competitors are hundreds of kilograms heavier: the BMW 7 series starts at 1,790kg, the Mercedes-Benz S-Class at 1,810kg and the Volkswagen Phaeton at 1,996kg.

Car makers such as BMW, PSA/Peugeot-Citroen and Renault use aluminium components in conventional steel body structures. BMW's new 5 series has an all-aluminium front-end body structure. The former version was made of steel.

Audi also uses aluminium parts in its A3, A4 and A6 models.

Despite the disadvantages, aluminium has definitely found a place in the motor industry. With widespread use of aluminium in castings, it accounts for 100kg of the average new car's weight. The aluminium industry expects that to grow to 200kg per vehicle by 2015.

For the same strength car body, aluminium is 55% lighter than steel, so aluminium structures use about half as much material. And as designers reduce overall vehicle weight, they can use smaller and lighter components elsewhere. Cut 100kg from a car body and it needs a less powerful engine and transmission, smaller brakes, and lighter suspension and tyres - so the weight saving from the lighter metal is compounded.