My commute is about 1.5 miles to work and takes about 6 - 8 minutes. We bought our HCH mostly because my wife is a professor at a University which is about a 45 mile commute. She only has to go there 2-3 days per week so I use it to commute on the other days instead of the CR-V that I typically drive.....

anyway when driving on my 1.5 mile commute I get around 40 mpg in the current spring/summer weather we are having. Over the winter I would get around 36/38 mpg on this commute since it took the entire drive for the car to warm up. My wife and i get around 45-48 mpg on longer trips and on her commute. Since you live in a warmer climate, you will see some benefit.... obviously a short commute will be hard on the mileage of any car.