To my knowledge they have not done away with the engine covers. The truck needs a cold weather package to get the cover with the truck. Let your fuel economy dictate whether to use it or not. I am in Detroit, and have had mine on for a couple of weeks. The fuel economy came right back once it was installed.
2006 2500HD LBZ 4X4 CC/SB LT3, 265/75R16, Rhino Liner, PCV Reroute, Resonator Plugged, 35w 6K HID Low Beam & Fog Lights, LED Interior Lights, ISSPro Pyro, Boost, & Rail Pressure Gauges in A-Pillar, Cognito Idler/Pitman supports, more to come soon.
1996 K2500 Suburban 7.4L, 265/75R16, Brush Guard, Nerf Bars