[slowbro]

What would be the best testing procedure to find significant results from aero mods? The other day, I was trying to test some mods made out of cardboard and duct-tape, and the results were inconclusive. I did A-B-A testing with the B runs as the mod and A being no change to the vehicle and did two A runs, followed by three B runs, and ending with two A runs. The changes in fuel economy seemed negligible and inconsistent. I think the natural variability in each of the runs caused there to be no significant difference. Would coast-down testing be better than just watching the fuel economy display (Scanguage) while holding a constant speed? Would I be able to see results better? Is there another way to test? I don't have cruise control in my car so the speed that I hold while using the fuel economy method is only as good as my ability to slightly alter my foot position as needed.
If someone could detail coast-down testing in their response, I would greatly appreciate it.