None of the "HHO" devices (i.e., the H-OH+ devices) sold to "increase gas mileage" work: they do not because they cannot, and the laws of physics and on-road testing show they do not work. Yes, it is a scam; no, you will not see any improvement in your automobile after installing such a device; yes, they actually waste gasoline since they force the automobile's alternator's field to be energized most of the time.

The people selling these devices do not use them, even though they will insist otherwise.

If you were defrauded into buying one of these devices, you probably feel foolish: that is not helpful--- the proper emotion is anger at being defrauded and deceived. Please help others avoid being robbed, and tell people on the 'net about your experience with being scammed.