A 2008 Chevrolet Malibu LTZ is shown equipped with a six-speed automatic transmission mated with a four-cylinder engine in Detroit, Tuesday, April 22, 2008. The new powertrain debuts immediately in the high-end Malibu LTZ, and next year in two lower-priced Malibu models. The LTZ's fuel economy, as estimated by the U.S. Environmental Protection Agency, is 32 miles per gallon on the highway, up from 30 mpg on the existing six-cylinder LTZ , and 22 mpg city. (AP Photo/Paul Sancya)

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