A few months back, we looked at a number of fuel-saving devices and found out that, not surprisingly, none of them worked. The Fuel Doctor FD-47 was one of these devices. After we published the story, Fuel Doctor president and CEO Mark Soffa repeatedly contacted us to challenge our testing methodology and claim that the FD-47 works as advertised. In the end, we conceded that the Fuel Doctor claims to work on vehicles more than two years old and our test was performed on newer cars. We promised to follow up.
Our next round of testing revolves around the actual function of the FD-47. The explanation of how the Fuel Doctor works boils down to three essential points: 1) As a vehicle gets older, the electrical ground deteriorates; 2) The deterioration of the ground causes electrical noise and interference that diminish the performance of the fuel injectors and/or ECU; and 3) The FD-47, plugged into a 12-volt port in a vehicle’s interior, conditions this noise and improves vehicle performance.
Left: A 13-volt DC current with the FD-47 disconnected. Right: The same 13-volt DC signal from the amplifier (orange) and across the FD-47 connection point (green). When connected, the FD-47 introduces about one volt peak-to-peak of noise.
It all sounds pretty far-fetched. ECUs are shielded from noise, both with respect to the ground wire and the other electrical components. But for the sake of argument, we decided to accept the theory that you can actually affect an engine’s ECU through the 12-volt power port. If this noise does occur, and that noise affects the ECU, and it can be fixed through the 12-volt port, does the FD-47 actually cancel any of it?
Left: The two signals superimposed, showing that the noise is slightly higher at the source (the FD-47). Right: A close-up look at the noise blips introduced by the FD-47.
No. Not at all. In fact, the FD-47 makes things worse. We bought a brand-new FD-47 Platinum from the Fuel Doctor website and sent it to an engineer for an automotive supplier to test the noise-damping characteristics of the device. Basically, we tried to recreate the graph shown on the “How it Works” page of the Fuel Doctor website. (At the time of publishing this, Fuel Doctor’s How it Works page is down; you can see an archived version here.) Our results, as you can see in the images here, show the exact opposite of the Fuel Doctor’s claims. To quote our engineer: “We concluded that the FD-47 does nothing to clean up the power noise in a vehicle, and in fact adds more noise.”
Left: A 0.5-volt peak-to-peak random noise signal with the FD-47 disconnected. Right: The same 0.5-v peak-to-peak noise signal with the FD-47 connected. The FD-47 (green) fails to filter out the white noise and in fact introduces the same additional noise seen before.
For reference, the test equipment consisted of a Hewlett-Packard 33120A waveform generator, Techron 7570 amplifier, Hewlett-Packard Infinium oscilloscope, and a Fluke 87V multimeter.
Superimposed images of the white noise plus the additional noise of the FD-47.
Still not convinced the FD-47 is a scam? Consumer Reports also performed an early test, also was challenged by Fuel Doctor, and also repeated its testing. In the second CR test, all of the recommended procedures were followed, including using older vehicles, and no meaningful improvement was found.
In short: Save your money instead of wasting it on the Fuel Doctor. Or waste it on something cool like this.
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