BMW AG is the first high-volume auto maker in decades to spec lightweight magnesium for a new engine block, which will make its U.S. debut in the all-new '06 3-Series.

This high-profile application, along with others including Mercedes-Benz's 7-speed automatic transmission case and the engine cradle for the new Chevrolet Corvette Z06, have officials at magnesium supplier Hydro Magnesium optimistic about the future.

The new BMW engine block, which features aluminum cylinder liners, is about 25% lighter than a comparable all-aluminum block.

That has other auto makers, including Audi AG, looking seriously at magnesium for structural engine components, says Dugald S. Reid, director-North America sales and marketing, for Hydro Magnesium's Norsk Hydro Canada Inc.

However, industry sources say that despite its light weight, high costs and concerns about its strength when the metal is subjected to high temperatures over extended periods have limited magnesium's role in vehicles — modern vehicles contain an average of 10 lbs. (4.5 kg) of magnesium, up from about 3 lbs. (1.4 kg) in the 1970s.

However, a new series of heat-resistant magnesium alloys, known as AE alloys, should enable magnesium to win more applications in future cars and trucks, Reid says.

These special alloys played a role in General Motors Corp. specifying magnesium for the 22-lb. (10-kg) engine cradle of the Corvette Z06, mainly because its location is very close to at least one of the 505-hp engine's catalytic converters, Reid says.

Hydro Magnesium officials expect more engine cradles in the future to be designed with magnesium in mind.