You might expect the Honda Fit to be the most fuel-efficient non-hybrid Honda makes. Although it looks the part, it's not true--the Civic is actually considerably better in EPA ratings, while the Fit gets a 35-mpg rating at best.
Manual transmission versions of the Honda Fit and Honda Fit Sport get 27 mpg in the city and 33 mpg on the highway. The base Honda Fit with the five-speed automatic fares slightly better, with EPA estimates of 28 mpg city and 35 mpg on the highway.
While those are good ratings, it's not particularly impressive in a class where 40 mpg highway ratings are becoming the norm.
Also of note on the green front is that there's a new Honda Fit EV offered for the first time this year. While this model offers good performance and a range of 82 miles, along with a rating of 118 MPG-equivalent, Honda only plans to build about 1,100 of these over three years, and offer them under a lease-only arrangement.