We bought aluminum wheels for ours. The aluminum ones we bought weigh the same as the steel original ones. There are probably ones that are lighter, but removing those things are not going to change your mileage much at all. Saving money on gas and hummers don't mix. lol.

 

An Efan conversion by itself will free up about 1MPG and costs less that a set of wheels.

Weight reduction by itself is not going to get you any change in MPG. My 2007 weighs about 5800# in full off road dress, I get 17.5-18 MPG everywhere all day, better on the highway. That is about 1000# above stock because of RR Sliders, Roc Doc U Bolt Skidz and Diff Cover, BA UPC and Winch Bumper.

Air Doc Intake, PCM tune, Cat back, Port Polished TB, Efan conversion with Mobil1 on 305 MTZ tires at 40PSI gets it done.