LOS ANGELES – GMC has rolled out its 2008 Yukon Hybrid with a two-mode system that combines hybrid technology with cylinder deactivation, according to Edmunds.com. The GMC hybrid, which features one mode for city driving and one for highway driving, will hit showrooms at the end of 2007. The Yukon Hybrid is expected to deliver a 25-percent improvement in the SUV’s fuel economy. The 2007 GMC Yukon 1500 2WD returns 16 mpg in city driving and 22 on the highway, according to the EPA. The Yukon Hybrid is powered by a Vortec V-8 engine capable of towing 6,000 lbs. To offset the weight from the hybrid system, certain Yukon components, such as the hood, front, and rear fascias, and grille, were redesigned. The first mode of the system is for low speed and light loads. In this mode, the hybrid system can operate with electric power only, engine power only, and any combination of engine and electric power, according to Edmunds.com. The Yukon Hybrid can operate exclusively under electric power at low speeds for extended periods of time. The second mode is used for highway speeds. It integrates electric assist, cylinder deactivation, cam phasing, and late-intake valve closure to allow more efficient engine operation. Full eight-cylinder power kicks in during situations such as passing, towing, or climbing a steep grade. GMC teamed up with DaimlerChrysler and BMW Group to co-develop the two-mode hybrid system.