What hurts your fuel economy driving a Suburban is a double whammy: very heavy weight, and poor aerodynamics. That wing is to help keep the rear window cleaner. Without it you will just have to clean the rear more often.
Other than trading to a more Fuel Efficient vehicle, there are plenty of things that you could do to save gas.
Drive less. Get a bicycle. If you live far from work, drive part way then bicycle. Do not let it idle for no reason. Maximum air pressure in tires. Do not allow the cavernous back of that thing become a rolling storage unit. Pretty much read the driving tips, and use as many as are practacle for you. I would advise against engine off coasting, just too dangerous in that kind of vehicle.
Keep in mind that everytime you take off from a stop it takes a large amount of energy to get that heavy thing moving. Taking your time with acceleration will help. Mashing the go pedal will burn lots of fuel, avoid it.
Later,
Allan Greenblazer
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