Tom Krisher
Associated Press
Aug. 25, 2006 12:00 AM

MILFORD, Mich. - Two electric motors, a V-8 engine that can work on only four cylinders, a really smart computer, and a four-speed transmission that joins them into one package.

GM calls it "dual hybrid" technology and says that soon it will make pickup trucks or big sport utility vehicles as fuel efficient as some cars.

The technology, showcased with General Motors Corp.'s future engines and powertrains Thursday at the company's proving grounds northwest of Detroit, will start showing up in the 2008 model year with the GMC Tahoe SUV. It will be available on the GMC Yukon and Cadillac Escalade SUVs and the Chevrolet Silverado pickup - GM's top-selling vehicle - later that year.
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GM says the hybrids, similar to those now in use in the transit buses of 39 cities, are so versatile that they will boost fuel economy by 25 percent over the current SUVs and pickups. For the two-wheel-drive Tahoe, which now gets an average of 18.3 miles per gallon in combined city-highway driving, that means nearly 23 mpg.

Figures for city and highway driving haven't been calculated yet, but Tim Grewe, GM's chief engineer for rear-wheel-drive powertrain hybrids, said there will be a significant improvement.

"We give you the highway economy and we give you the city economy while maintaining SUV performance," he said.

The dual hybrids, developed jointly by thousands of engineers with GM, DaimlerChrysler AG and BMW AG, also will be placed in the Dodge Durango and BMW vehicles.

Prices on the GM vehicles haven't been set, Grewe said, but the company plans to make them competitive, similar to a $2,000 premium on the hybrid version of the Saturn Vue.

Most current hybrids are efficient in stop-and-start city driving, but they aren't as efficient at highway speeds. The new technology uses a computer to choose from thousands of combinations of running on one electric motor, two electric motors, a combination of electric motors and the V-8 gasoline engine, or shutting down some of the V-8's cylinders.

The computer judges speed, the load the vehicle is pulling, terrain, temperature and humidity, whether the pavement is wet and other factors to decide the most fuel-efficient combination of technologies.

"It's got a gazillion choices to make, and it makes them 100 times a second," Grewe said. "It's like having the world's smartest co-pilot."