Damn you must drive it like once a week if you haven't had to fill it all month. I get 26mpg and buy the premium non-ethanol 91 fuel and still fill my car twice a week.
I live in a country town, so driving places doesn't use as much gas as driving in a city, not to mention I'm driving what is essentially the late 2000's equivalent of a Geo Metro. Except more fun.
Funnily enough, my parents bought this car because their Geo Metro got totalled in a walmart parking lot. This was in 2006 shortly before the value hiked, so that sucked.