[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.

[Pete from Shawnee Mission]

"So you wind up with magnesium hydroxide byproduct."

Nifty! So if this works, you get H2 to power your car,and the the byproduct is milk of magnesia! Save the environment and cure upset stomachs as you drive!