Burning 1 gallon of gasoline produces 1.52 gallons of water. How this is calculated:1 gallon of gasoline weights 8.66lbs, of which 1.4 lbs is Hydrogen, as gasoline contains 16% Hydrogen and 84% carbon by weight.This assumes gasoline has the chemical formula of C8H18, the same as Octane.Water is 11% Hydrogen and 89% Oxygen by weight. One gallon of water weights 8.35lbs, and contains .92 lbs of Hydrogen, and 7.43 lbs of oxygen.Therefore since hydrogen burned or in, equals hydrogen out after combustion, therefore 1.4 lbs of hydrogen burned, equals 1.4 lbs of hydrogen in the H20 or water created in combustion. By weight, 1.4 lbs of hydrogen divided by the weight of .92 lbs of hydrogen in water, equals 1.52. So 1.4 lbs of hydrogen in 1 gallon of gasoline, is converted to more gallons of water because gasoline contains more hydrogen per gallon, then does water.