Fuel Doctor

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Fuel Doctor 'FD-47 Platinum'.
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The Fuel Doctor has been showing up at major retailers and convenience stores, costing $50 to $60. So we thought it warranted review. When we put it through our extensive testing on a number of vehicles, we found that it made no significant difference in any evaluation. As far as we can tell, all it does is light up when it’s plugged in.
Consumer Reports, 2010[1]

Fuel Doctor is a junk product that claims to increase fuel efficiency by smoothing the DC voltage of a vehicle's electronic injection system just by sticking a dildo with some flashing lights into the cigarette lighter.[2][3] It's a prime example of automotive woo.

What is it?[edit]

The Fuel Doctor comes in just one model, the 'FD-47 Platinum'; although why it should be given the Platinum moniker is anybody's guess. The makers claim that:

The Fuel Doctor’s FD-47 conditions the Power Systems optimizing a motor vehicle’s electronic systems. Similar to how high end entertainment systems filter the current’s electrical noise, the Fuel Doctor works by stabilizing the voltage running through your car or truck’s ECU.

Various other sales outlets describe the product:

The device simply plugs into a vehicle's DC outlet and stabilizes the electrical current flowing to the electrical control unit (ECU)--the computer that controls the engine's fuel injection and ignition systems--to optimize engine efficiency and improve gas mileage. It also mitigates electrical interference from the stereo, lights, or air conditioning that can negatively affect the ECU's ability to optimize fuel injection and fuel efficiency.[3]

However it's not all woo. The thing's caveats include:

It also takes time for the vehicle’s electronics to adjust to the cleaner signals as a result of the FD-47 power conditioning.[4]

Ah yes, electronic circuits have feelings too.

Smarmy webshites[edit]

We welcome your opinion! (Not!)

In 2011, an internet search for "Fuel Doctor scam" brought up a now-defunct site called (unoriginally) "FuelDoctorScam.com" which contained only positive reviews of the product.[5] A DomainTools search showed that the registrant was Fuel Doctor, obviously an attempt to pre-empt the expected criticism. Should you wish to contribute your own review at FuelDoctorScam, then don't be surprised if it is never posted. Despite that, the positive reviews all get overwhelmingly 'dislike' votes.

The perpetrators of this scam appear to have created at least one other suspicious webshite, full of fake product reviews and links to a $5 coupon and a "store locator".[6]

Similar products[edit]

No, it's not an adult toy; it just looks like one.
..the Fuelshark does absolutely nothing beyond casting a novel blue glow in your footwell.
—Jason Torchinsky, "Fuelshark Wants Us To Apologize Because They Sell Bullshit", Jalopnik, 2014[7]

The Fuel Shark is an amazingly similar and equally spurious product that looks even more like a feminine massage device than the Fuel Doctor, and at a cheaper price.[8][9] The Fuel Shark's woo is at least based in reality, however. Fuel Shark claims to use a capacitor to store energy to run your car's electrical systems, thereby taking load off the motor, especially at idle. Mazda has recently employed this technique, and it has caused a significant increase in fuel economy as part of its SkyActiv system. However, the capacitor in the Fuel Shark is orders of magnitude too small to have any effect whatsoever. Mazda's capacitor is rated at 120 farads of capacitance. Fuel Shark's is rated at 1000 microfarads.

What this means, to anyone with any knowledge of electronics, is that the Fuel Shark is simply incapable of running any of the car's electrical systems for any significant period of time. The capacitor used by Mazda is a whopping 120,000 times more capacitive, and it is likely the smallest capacitor possible for this system, given that larger capacitors are more expensive. In Mazda's case, the capacitor is but one part of a larger system designed to recover, store and distribute previously wasted braking energy, including such parts as a variable voltage alternator and a DC/DC converter, neither of which are included with a Fuel Shark.

In other words, the Fuel Shark is a 7 cent capacitor with an LED light attached to it which does a lump total of nothing. Despite this, this damned useless thing is available at Wal-Mart, Amazon, and other purveyors of fine woo.

External links[edit]


  1. Fuel Doctor FD-47 fails the Consumer Reports mpg test. Archived from Consumer Reports, 7 December 2010,
  2. Fuel Doctor online store. Archived from store.fueldoctorusa.com, 7 July 2013.
  3. 3.0 3.1 Hammacher Schlemmer (now discontinued)
  4. Why Did Consumer Reports Label FD-47 as a “Don’t Buy”? Archived from fueldoctorusa.com, 30 September 2013.
  5. Fuel Doctor Scam. Archived from fueldoctorscam.com, (September 18, 2011 archived copy)
  6. Fuel Doctor Reviews. Archived from fueldoctorreviews.com, 7 July 2013.
  7. Jason Torchinsky, Fuelshark Wants Us To Apologize Because They Sell Bullshit. Jalopnik, 21 February 2014.
  8. Fuel Shark Cigarette Lighter Fuel Saver Review / Teardown. Perfrormance Chip Guide, 2020.
  9. Antony Ingram, Fuel Shark gadget to boost gas mileage does nothing of the sort. Green Carpet Reports, 25 February 2014.