By NEAL E. BOUDETTE and MIKE RAMSEY
Wall Street Journal
DETROIT—Auto makers wrestling with ambitious mileage goals have touted hybrids and electrics as the wave of the future, but they have found a quicker path to improved fuel efficiency, reinventing the way traditional gas-powered cars are built.
For the past century, autos were made largely of steel. But pressed to produce cars and trucks that go farther on a gallon of gas, manufacturers gathering here this week for the Motor City's annual auto show are cutting weight by substituting more plastics, aluminum and magnesium, including materials once found only in high-end race cars.
Only a handful of parts fashioned from new, lightweight materials are in current models—for example, the magnesium tailgate of the Explorer, the sport utility vehicle from Ford Motor Co. But in four to six years, car companies will roll out vehicles completely redesigned to use a wide mix of specialized materials.