2006 Crew Cab 6.0 4WD.. This thing gets 9 mpg and drops when I'm at a stop light. Help please any ideas will help. I don't stomp on it, I drive light, let it warm up, all stock. Driving around it will go up, 9.8 9.9 10.0 but as soon as I stop instantly it goes 10.0 9.9 9.8 etc.. This is on the Edge CTS and the Dash "Lie O Meter" stays pretty consistent with the Edge CTS with the MPG read out. Thanks!