Lean burn.
The best thing since sliced bread and everyone wants it. You have your 5th gen Civic VX, 6th gen Civic HX, and your 1st gen Insight and then it was eliminated for emissions (?) reasons.
But wait, there's more! From 2001-2005 they continued making the HX. It has a 117hp 1.7L VTEC-E engine with lean burn. .gov currently rates it at 31/39mpg. And here is the one I own:
I bought it this summer and first fixed a bunch of the problems that made it quite cheap (like replacing the pass. door that the original owner's angry ex-boyfriend scribbled "B*tch" in). Started commuting in it and was getting 40mpg in warm summer temps and light traffic.
First mod, a grill block:
This is blocking too much air for summer, but I am leaving it during the winter months.