I think you should buy two of them. That would give a 30MPG improvement, which would cause the gas tank to overflow. You could then use the overflow gas in the lawn mower.

Sorry to be a wiseA$$, but these kind of scams just set me off. If such a thing actually did what it claimed, don't you think that it would be worth a little more than $10? It would probably be worth at least $15.

If there was a way to accomplish whatever this is supposed to accomplish, I feel QUITE confident that the engineers in that tall building in Stuttgart would have figured it out YEARS ago.