what can I do to increase the gas mileage
Ha, buy a Hybrid. But seriously, nothing you can do will help in MPG on a Hummer H2. Only thing I can recommend is keep the truck running in top condition, and the tires at the proper pressure. You probably won't notice any change.
Drive slower, smoother, don't push the accelerator past half throttle, just start CRUISIN' it- it is a state of mind and there are internet videos which show how mileage champions drive-
* Smooth acceleration and smooth stopping. * Higher speeds at lower RPM will increase gas mileage. * Keep maintenance current. (Oil/Filters, Sparkplugs & wires, tire pressure). This being said, you would at most only improve by 2-3 MPG.
Looking for a Used H2 in your area?
CarGurus has 1,300 nationwide H2 listings starting at $6,000.
Search Hummer H2 Questions
Hummer H2 Experts