Powered by Honda’s so-called K-Series engine, the 2006 Honda Civic Si has a 2.0-liter, DOHC, i-VTEC motor under the hood that makes 197 horsepower at 7,800 rpm and 139 lb.-ft. of torque at 6,200 rpm. Redline is 8,000 rpm, and a warning light flashes in the gauge cluster when that limit is approaching. Meeting LEV2-LEV emissions in the U.S., this engine is estimated to deliver 22 mpg in the city and 31 mpg on the highway. Premium fuel is required.