Wow I have a headache from over info but the best method to improve fuel economy is in your garage probably FREE Can be installed with hand tools.Will take about 10 minutes. Want to know how? OK here it is ............ Take a piece of plwywood 1" wide and 2" long fine the area that the gas peddal is the lowest screw the plywood to the floor boards preventing the gas peddal from being fully depressed. Amazing gas milage is improved bad side effect loss of top speed and power, but I only claimed to be able to improve fuel economy lol. Sorry off track but I thought at this point a tiny bit of humour might help at the gas pumps.