When burning a gallon of gasoline how much water is created?

Question

When burning a gallon of gasoline how much water is created?

Answer 1

The example below is made assuming using pure octane (C8H18).  Gasoline is a mixture of several types of hydrocarbons.  The exact amount of water produced will vary based on the exact products involved.  It would be fairly involved to show exactly what a particular blend would produce, as some products will produce more water per unit weight than octane, will others would produce less water.

So, for the pure octane mixture, burning a pound of octane will produce 3.08 pounds of carbon dioxide and 1.42 pounds of water.

A gallon of octane weighs 5.86 pounds, so that will yield 18.1 pounds of carbon dioxide and 8.32 pounds of water upon combustion.  

So, burning one gallon of pure octane will produce approximately 1 gallon of water.