Here is a site with some gas saving tips:
http://forum.ecomodder.com/showthread.php?t=44

Section 4; item #8 caught my eye. ;"Take off the alternator belt".
   Instead of something that drastic I was thinkng of adding a circuit loop
to disable/enable the alternator on my daily driver . Some sites claim 5 to
10% fuel savings.
Spit-balling:
The alternator would only be loaded during:
1> braking
2>battery voltage below 11(?) volts
3>button on shifter activation for downshifting
4>?

Otherwise the ignition system would run on the spare battery . Solar panels
could charge it during the day between commutes. All parts I have laying
around the garage. Hmmmm....

Ken Lewis
http://neksiwel.20m.com/