interesting idea, the only problem that I see is you may have many disappointed drivers of lower mpg cars (SUVs, trucks, etc). I have employed the methods mentioned on this site (aside from turning off my vehicle while driving) and have only seen a modest gain in mpg (2-3). When time comes to turn the AC off, I may see a bigger jump, but not until then.

Anyway, good luck and let us know how it goes.

19,900 miles and (slowly) counting