Maintenance is of course a big factor, but driving style is my #1. Being efficient does NOT necessarily involve driving slow. Read traffic patterns, keep your speed constant -- and take advantage of coasting. There isn't a point to stay on the throttle the extra few seconds as you're approaching the same red light.
- Where speeds permit, I try as much as possible to cruise just
inside TC lockup speed, or about 40mph.
- Build your speed on downhill sections, and keep throttle input to a minimum. This'll allow you to lose speed on following uphills without falling too far back. Shut off cruise when going uphill.
Most recent tank on the Civic was just above 36mpg (6.5L/100km).
edit: At $1.20/L, which is where Toronto is right now - this is equivalent to $4.51 USD per US gallon. I drive 23,000km a year, which is 14,200 miles. The difference between 30 and 25mpg is $433 a year. 22 versus 17mpg? $870. That'* a lot of beer!