Like sister brand Chevrolet, GMC offered a light hybrid version of its Sierra full-size pickup for the 2005-2007 model years. That system was limited, only offering engine idle shutoff; it improved fuel economy by maybe 8 percent. At the 2007 Los Angeles Auto Show, Chevrolet announced a new, more substantial two-mode hybrid version of the Silverado for the 2009 model year. Now GMC is following suit.