Stop-start technology, which Ford already has used on hybrids, saves fuel by shutting off the engine when the vehicle comes to a stop in traffic or at a red light. Ford estimates customers who buy the Fusion with stop-start will save $1,100 in gasoline outlays over five years of driving. The $295 option will be offered only on 2013 Ford Fusions powered by a 1.6-liter, four-cylinder EcoBoost engine,