For those who like the Civic Sedan's packaging but want top-tier fuel economy—and maybe have a slightly larger budget—the Civic Hybrid is the pick of the lineup; with Honda's IMA mild-hybrid system, it achieves an EPA-rated 40 mpg city, 43 highway.
Civic Si models aren't nearly as good. Because of their deeper-breathing engine and lower gear ratios, which keep the engine revving, the Civic Si returns numbers in the low to mid 20s, according to our driving experience. That's not particularly green, even compared to other sport coupes.
There's also a limited-production natural gas version of the Civic, the GX. Honda says natural gas is about 35 percent cheaper than gasoline, and the Civic GX gets the gasoline equivalent of 24 mpg city, 36 highway, so you'll pay off any premium quite quickly. It's probably not the best choice for long-distance driving, however.