welcome to the site, there many knowledgeable ecomodders here.
here is a site which may answer some of your gimmick questions,
http://www.fuelsaving.info/index.htm
BTW what is the gas price in Hawaii, we feel bad about $3-4 here.
Adjusted for inflation its the highest since 1981. which i remember well cause my adjustable mortgage when to 12% and i got laid off. those were the good old days.