And there are other options too
There are 4 good lectures here...
http://www.waterfuelcell.org/
1st movie suggest HHO can be created in abundance with less than 0.5 amp!!! using frequency and high voltage in a pulsed circuit...
And also as ebay will show by typing in 'HHO' petrol / diesel cars can be improved no end. I'm investigating this further with friends