God, there really are some fuddy duddy old men out ther in internet-land, aren't there?
I have stood in a garage, for 15 minutes, while a petrol engine was running, and I didn't choke to death. Why? Because it was running partly on water.
Search Swedish/Norweigian websites for this stuff if you are serious about saving fuel. Look into what they did in the second world war and before, with fuelling vehicles - really cool stuff, and when Armageddon comes you'll be better placed.
Or rather your children and grandchildren will stand a chance. We have blown it, but why stuff the future generations?