Members here know about my 25-mile freeway work commute. My fuel economy is much better in the mornings than the evenings.
In the mornings, shead of the ruch hour, I can generally do a steady 60mph. When traffic pools up, I can usually anticipate and make the FE damage mimimal.
In the evenings, the rush hour traffic makes going 60mph nearly impossible. Compounded to my typical 70mph evening cruise speed, I occasionally fall prey to "The Dark Side" in regards to agressive drivers.
If you cruise over 65mph, FE will take a hit for sure due to increased wind resistance. If your Civic has lean burn, it won't work at that higher speed.
Going on a non-freeway route at 45mph can deliver good FE if you can anticipate the lights and traffic. Sometimes I'll take such a route right after work to the gym. Nice thing after the work out - rush hour is over.
