Background - the car & aero influences

My car is a 1992 Honda Civic CX which I bought new, has an EPA fuel consumption rating of 47 mpg (US) highway / 39 city (5.0/6.0 L/100 km ... 20.0/16.6 km/L ... 56.4/46.8 mpg (Imp.)), and averaged mid 40's when driven "normally".

Before Katrina, I had been using hypermiling techniques to get me up to an average in the high 50's, but I had to keep the speed below 55 mph (89 km/h) to achieve it, which can be inconvenient to do on busy highways. About this time I had read Phil Knox's article "Free Fuel Riding on the Wind" in EV World where he talked about using commonplace materials from the local hardware store to lower his truck's drag coefficient (Cd) and improve its gas mileage at highway speeds. Also, having lived in Germany, I was familiar with many of the ultra-low Cd cars designed in Germany during the 1930's.

Since it didn't look like the car companies were planning to do anything in the foreseeable future about introducing a small car that would get good fuel economy on the highway, I decided to see what I could do towards improving my existing car's gas mileage.