GM's Changing Philosophy
The Enclave mentioned in the opening was released by General Motors well before the big rise in gas prices in the spring of 2008. It is a good example of positioning a vehicle before market shifts and declining sales force a change.
Interestingly, GM power plants, such as the 6.2-liter V8 in the 2008 Chevrolet Corvette can also deliver respectable gas mileage, up to 26 mpg on the highway with a stick shift.
Sam Winegarden, GM's executive director of engine engineering, said GM designers are solving the problem by "virtually working it from the entire vehicle perspective." He mentioned improved aerodynamics, reducing weight by the use of premium materials and producing the lowest rolling resistance. He emphatically added, "We want to give the customer the best fuel economy and not sacrifice performance."
When it comes to the powertrain side of the equation, "we need to make a big engine look small," Winegarden said. This means that a V8 is designed with what GM calls "active fuel management" which, depending on load, will run on four of its eight cylinders, such as in the 2007 Chevrolet Tahoe we used for a fuel economy test.
Besides these innovations, Winegarden said GM is planning to increase its "hybrid portfolio" and to look to its overseas fleet for new diesel technology. He pointed to the tuning of the current Cobalt to produce the XFE model that gets 36 mpg highway, calling it the "playing out of some advanced technology functions." Another example is the downsized direct injection used in the Chevrolet HHR SS. "It has pretty awesome performance with good fuel," he said.