idk, I know with avgas (100octane low lead) it weights 6lbs. per gallon. I've heard anywhere from 5.5 to 6.5 for regular fuel but if you use that 6lbs. then our 13 gallon tanks will hold 78 lbs of fuel. Having half a tank reduces the weight by 39lbs. not much of a difference but the question is: is it worth it to have to stop twice as often to lighten the car by the weight of a small child?
2006 Red Chevy Cobalt LT
mods: Kenwood DNX5140 Head Unit, HIDs, Halo headlights, LED taillights, Injen CAI, LSJ throttle body, 2.4L intake manifold, red interior LED's, TWM short shifter, custom fit red seat covers, red trim and door handles, SS gauge cluster, Racing Solution long tube header/downpipe, Corsa touring exhaust, lightweight crank and alternator pulleys, trifecta tune, 17" Motegi black rims