To help reduce vehicle weight aluminium is becoming more important for German auto maker BMW and its use of the metal has grown steadily in recent years, the company told Reuters.

Car makers around the world are on a mission to reduce the weight of cars to promote fuel efficiency and aluminium fits the bill as it is lighter than steel and sustainable because it can be recycled.

"The most significant changes were the introduction of aluminium doors and hoods in some models as well as casted structural components," said Frank Wienstroth, who overseas BMW's communications on the supply chain and sustainability.

"The application of aluminium varies significantly between different models. As an example for a typical BMW premium car the new Five Series has aluminium parts summing up to almost 20 percent of the vehicle weight," he said this week.

The world's largest premium car maker recently detailed plans to take its Five Series ActiveHybrid concept into full-scale production as early as next year.

Aluminium recycling rates in the transport sector are estimated at more than 90 percent. In the building sector the number is 95 percent and in packaging it is thought to be much lower at around 35 percent.

The average car weighs about 1,200-1,400 kg, containing around 500-700 kg steel, according to Jaguar Land Rover. Aluminium tends to be used in wheels and hoods.

Use of lighter aluminium also leads to other savings such as less wear and tear.

BMW earlier this week posted its best ever quarterly pre-tax profit, lifted by surging sales of luxury cars in China, the relaunch of its lucrative 5 Series saloon and a weaker euro currency.

HIGH STRENGTH STEEL

Steel is the most important material in BMW's "conventional" vehicles, accounting for about 40 percent of weight. BMW does not expect that to change over coming years.

But in the future, to make some of its vehicles lighter, steel will be substituted with lighter materials such as aluminium, plastics and carbon fibre laminates would continue.

"The lightweight strategies depend on the vehicle segment and the type of drive. In higher segments and for electric cars a more extensive use of lightweight parts is to be expected," Wienstroth said.

Higher segments is a reference to larger cars.

Electric cars are a big theme in a world currently focused on energy conservation and climate change.

BMW last year said it would launch a new class of environmentally friendly vehicles under its own brand, signalling that even premium automakers are ready to embrace electric vehicles as a mainstream product.

On the subject of lighter, higher strength steel, BMW said: "Regarding cost optimisation in weight reduction the weight advantage of aluminium can be equalized by new steel characteristics at lower material costs."

Some auto makers worry about using aluminium in their cars because of price volatility. Some say they could be persuaded if they could get long term deals with producers.

Benchmark aluminium prices on the London Metal Exchange have ranged between $1,300 and $2,400 a tonne since the first quarter on 2009 when markets started to fear economic recession could turn into a 1930s style depression.

Global consumption of aluminium this year is estimated at about 37 million tonnes.