The Fuel Doctor FD-47 Fuel Efficiency Booster is the revolutionary way to fight back high gas prices with a simple plug-in adapter. Help the environment by reducing emissions, and save money at the same time by increasing fuel economy. FD-47 stops interference that prevents your car’s electronic control unit from sending out steady current. Certified lab and field test show increased MPG of up to 25%. Free FB-28 12 Volt Car Adapter Splitter with your order. Plug two devices into your car’s power outlet.