FORTUNE -- Remember this exchange from 1967's The Graduate?
Mr. McGuire: I just want to say one word to you. Just one word.
Benjamin Braddock: Yes, sir.
Mr. McGuire: Are you listening?
Benjamin: Yes, I am.
Mr. McGuire: Plastics.
These days, if Ben were to get advice from Mr. McGuire about a new field to stake his future on, the answer could be "carbon fiber."
The miracle material, two-thirds the weight of steel yet five times stronger, is increasingly finding its way into automobiles. If a means can be found to use it in mass-production vehicles, it would result in dramatically improved fuel economy without resorting to exotic new fuels and engine technologies. Replacing the steel in a car with carbon fiber would shave hundreds of pounds off its weight.
Automakers are betting they can make it work, BMW in particular. After jetting into New York from Munich last week for a retirement dinner, BMW chairman Norbert Reithofer kept heading west to Washington State, tacking another 6,000 miles onto his trip to open a new factory there co-owned by BMW that manufactures carbon fibers. That's a lot of frequent flyer miles for an unproven technology.
Carbon fiber consists of thin strands of carbon woven into a yarn that in turn can be made into cloth. The cloth in turn is then laid over a mold and stiffened with resin to produce a sheet of material with remarkable properties.
Carbon fiber has found its way into fishing rods and tennis rackets, and in larger quantities into airplanes like the Boeing 787 Dreamliner and the bodies of Formula One racecars. A couple of high-end performance cars like the BMW M6 and Chevrolet Corvette have carbon fiber body panels, and the material is used for interior trim in the place of wood veneers or aluminum.
But high-volume applications have eluded carbon fibers. For one thing, the material is expensive. According to published estimates, carbon fiber costs about $10 a pound. That's a lot cheaper than the $150 a pound it cost a decade ago but still ten to 20 times more than a pound of steel.
For another, the construction process is laborious and can't easily be scaled up. Curing time can take hours. Moreover, carbon fibers can't be recycled because carbon composites don't corrode.
That hasn't deterred BMW, which is investing $100 million to build a carbon fiber factory in Washington State, 180 miles east of Seattle. The factory is co-owned and operated by a German company, SGL Carbon SE. Production of carbon fiber thread is starting this month. The fibers will be processed into lightweight fabrics at a second joint venture site in Germany.
Other German automakers are following right along. To make sure that it wasn't left out, archrival Volkswagen, maker of Audi, has bought a 9.9% stake in the SGL venture. Mercedes-Benz is jumping into the carbon fiber pool as well. It is building its own manufacturing facility in Germany in cooperation with a Japanese company. Mercedes has a goal of reducing vehicle structure weight by 10% with each succeeding generation, according to Bloomberg.
All three companies have some catching up to do. Tiny McLaren, based in the U.K., plans to use a carbon fiber chassis as the basis for 1,000 MP4-12C sports cars it plans to build this year. Base price: $231,400.
BMW is using carbon fiber in two futuristic cars it is introducing in 2013. A new process, operated mostly by robots, can turn out parts in a matter of minutes using injection molding. The automaker's models range from Mini Coopers to Rolls-Royces, but neither new car is anything like what it has built previously.
The i3, which carries four passengers, will be powered by either an electric or gasoline engine, and will weigh just 2,700 pounds -- about 20% less than a Nissan Leaf. BMW plans to make 30,000 i3s a year, Automotive News reports, for use in urban areas The i8, with both gas and electric motors, will be faster than a Ferrari and still be capable of 20 miles per electric charge, or 50 miles per gallon of gas.
Neither auto will be cheap. Bill Howard of ExtremeTech estimates the i3 will go for $50,000, and BMW has priced the i8 at around $170,000. By comparison, the Chevy Volt goes for $43,000, while the Tesla roadster sells for $109,000.
Says BMW's Reithofer, "Carbon fibers are a key construction material for the automotive industry of the 21st century and will change the way we develop and build cars."
What he didn't mention is the key advantage they have over other gas-saving technologies: They are here today -- not off in some gauzy future like solar power, natural gas, or hydrogen-based fuel cells. 
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