Here are a few practical tips to save fuel:
We Test the Tips 12 Proven Ways To Improve Gas Mileage 
PS. Gas is statistically cheaper on Wednesdays - then there is this one- gas up at night-
Buy gas during the coolest times of the day
“During these times gasoline is densest. Keep in mind - gas pumps measure volumes of gasoline, not densities of fuel concentration. You are charged according to ‘volume of measurement’.” [via HowToAdvice.com]