Not a scam as it includes a water separator. Beyond that I really have my doubts.

Low price to get you in the door but then you have to buy their replacement fuel filter.

The way of the human condition. If you expect to see improvement you can imagine it. I can think of no way this can increase fuel milage unless your old filter is obstructed. I base this on many people claiming a 1-2 mile improvement just by changing out an old fuel filter.