Honda’s compact Civic lineup expands in two directions for the 2007 model year. At one extreme is the new natural gas-powered Civic GX, and at the other a sporty Civic Si sedan that joins the already-on-sale Civic Si coupe. Other than the new models, there are few changes for the Civic for 2007, which entered its eighth generation with an all-new version for the 2006 model year.