The U.S. government’s Environmental Protection Agency gives it a failing grade. To sum up, for the health of your bank balance as well as for the health of the environment, Don’ t buy a Hummer. Hummer are big gas hogs. There are at least two reasons for not buying the huge, military-type vehicle called a Hummer. First, Hummers are bad for the environment. When gas cots $ 3 per gallon, it costs $ 100 to fill up a Hummer big gas tank. Second, The H2 model gets less than 10 miles per gallon of bas. In one year, a Hummer gives off 24100 pounds of carbon dioxide, which is two to three times more than average cars give off.