[Pete from Shawnee Mission]

If this works the question has to be not how many miles to the gallon of water, rather how many miles from a pound of Magnesium.

Found this for $46;

"Magnesium Plate .500" x 12" x 12" - AZ31B
AZ31B magnesium alloy machines easily. It is commonly used as an alternative to aluminum alloys due to its high strength to weight ratio. Care must be taken in machining the grade, however, because the chips and powder can be flammable.

And of course it would be good to know the byproduct of the reaction. Just for fun, chemists any thoughts?

[HangThemHigh]

Mg + 2H2O -> Mg(OH)2 + H2 (gas)

So you wind up with magnesium hydroxide byproduct.

Aluminum is probably cheaper and not quite as dangerous. But in a powdered unoxidized state, is still dangerous stuff.