The Fuel Doctor FD-47 Is More Of A Fuel-Savings Quack

A basic understanding of physics should tell you that the Fuel Doctor–a small device that you plug into the 12-volt power outlet in your car–will not work. The gadget claims that by “conditioning” your car’s electrical systems, it increases power and gas mileage. But…why have none of the major automakers thought of this? Is it all a plot between the car and gas companies… or is the Fuel Doctor just automotive snake oil?

To find out, Consumer Reports plugged the device in to cars set up with sensitive fuel mileage meters, and also tested the vehicles’ power with and without the Fuel Doctor. Their verdict? Well, there are some pretty red and green lights on the Fuel Doctor, so it makes a festive holiday decoration. That’s about it.

Fuel Doctor FD-47 fails the Consumer Reports mpg test [Consumer Reports Cars]


Edit Your Comment

  1. SkokieGuy says:

    Gee, if only the government could somehow find a way to protect consumers from fraudulent claims and defective products.

    I also suspect that Mr. Fuel is not really an MD.

  2. Mr. Fix-It says: "Canadian Bacon is best bacon!" says:

    More Automotive Quackery.

    On an unrelated note, I hear Snake Oil makes a great fuel additive.

    • jeffbone says:

      I don’t know about that, but for some reason my mechanic keeps recommending a blinker fluid flush, and now he says my muffler bearings are shot. All this right before Christmas, too…

  3. Snarkster says:

    Did CU get the second FD-47 for only the added cost of shipping and handling?

    What is the meaning of the 47?

    • Loias supports harsher punishments against corporations says:

      The number of counts of fraud and forgery they will be indicted with.

      • Excuse My Ambition Deficit Disorder says:

        They will not be able to touch them as they are located in North Korea…by the way they also sell x-ray glasses so you can “see” the savings….

    • MaxH42 thinks RecordStoreToughGuy got a raw deal says:

      It’s 7 better than WD-40!!11!!one!

      (I seriously do wonder if they intended for people to make that connection subconsciously.)

    • stormbird says:

      There’s a running… not quite gag within Star Trek about 47. It keeps showing up in starship numbers and coordinates and sectors and number of people being turned into Borg. With the misspellings and confusion between ‘affects’ and ‘effects’, it’s possible we have a copy writer that’s a frustrated Trekkie.

  4. Sonicjosh says:

    Why am I not surprised in the slightest?

  5. mike says:

    I’d like to see someone actually take the device apart and see what’s inside. My guess is it just has a circuit board that lights up the LEDs randomly.

    • He says:

      Ditto to this. I didn’t care about the tests, but I always like seeing what’s inside blatantly fake devices. Send those things to sparkfun or hackaday

      • SkullCowboy says:

        Go here for a look at the internals on this miraculous device. :)

        • Mr. Fix-It says: "Canadian Bacon is best bacon!" says:

          I’ve only a passing knowledge in Micro-circuitry, but that looks like it don’t do shit!

          • MrEvil says:

            There’s nothing micro about these things. It’s just a simple circuit to let LED’s light up. It has a voltage regulator that doesn’t do anything other than sit on the PCB.

            • vastrightwing says:

              I can’t figure out why on earth they would build such a complicated circuit to light up a few LEDs. Seems to me they could have easily mounted 3 LEDS with some resisters and left it at that. I mean, they’re taking a lot of profit away by adding needless components and complexity to it. Or, perhaps, this is the equivalent of obfuscating the circuit so people think it’s doing something. But how many people are going to tear the thing apart to find out?

        • mike says:

          Awesome! This basically, this is a dumbed down version of a voltage detector.

          Well, you know what they say: A fool and his money are easily seperated.

    • shepd says:

      Here’s the list of parts I’d put in it:

      – 741 OpAmp
      – 3 resistors (3 x 1k)
      – 7812 Voltage Regulator
      – 1 capacitor (Ohh, let’s say 1000 uF @ 25 VDC)

      The OpAmp would give you battery high/low (yeah, there’s easier ways to do it, but you can’t beat a single line item that is super common!). 3 x 1k resistors for the LEDs. 7812 for a stable voltage reference for the OpAmp. Capacitor because you can then claim it “cleans” the power, but a capacitor that wimpy is, of course, absolutely pointless for the entire electrical system.

      • kc2idf says:

        Ooh! I like it! Set that up, and every time the car’s electrical system surges from the engine speeding up, it can take that cue to change the light from red to green, and vice-versa when you idle.


      • Eviile says:

        Let alone that I’m fairly sure that your ignition system isn’t tied into your cigarette lighter.

  6. Megalomania says:

    I can’t improve gas mileage by plugging something into my car-hole? This is no longer a world I want to live in.

  7. Cheap Sniveler: Sponsored by JustAnswer.comâ„¢ says:

    Surprisingly, someone MUST be buying it.

    Even more surprising, some of them probably came back for more.

  8. BeyondtheTech says:

    The new CSPC should be able to burn companies and con artists like these at the stake.

  9. KillerBee says:


    If you are stupid enough to fall for this, you deserve what you get.

    • BeyondtheTech says:

      There has to be a limit to “you deserve it.” HFCS rebranding itself as “corn sugar,” cereals that prevent heart disease, nearly all of the weight-loss products out there, McDonald’s chicken nuggets, partially-hydrogenated products, the grocery shrink ray, you name it – companies have done everything from illegal to immoral because they think or can get away with it. Even if it scams just a few hundred customers, it was worth their time and money to do so, and that’s gotta stop.

      • YouDidWhatNow? says:

        “There has to be a limit to “you deserve it.””

        No there doesn’t. Stupid should be punished. The problem is that people frequently don’t recognize that they’ve been stupid, and refuse to change their stupid ways. I attribute this phenomenon to the fact that they are stupid.

        • Shadowfax says:

          OK, but to play devil’s advocate, where do you draw the line? We’ve gone far beyond the point where any one person can know enough about everything to avoid getting duped. Look at the Tornado fuel saver piece of crap. They tell you just enough fake physics to make the product make sense, unless you are an engineer or a physics junkie. The average person is going to see that vortex-induced fast drain of the 2 liter Coke bottle and think “well hell, if it works for that, it’ll work in my car!” without realizing that even if it did work, there’s a 90 degree bend somewhere in the intake that will eliminate any vortex that you set up.

          Same thing with this – unless you understand electricity enough to realize that “conditioning” the power doesn’t reduce power consumption, you’re not likely to realize on the surface that this thing is a fraud.

          Sure, we should be using the logic of “if it worked, why isn’t it standard equipment,” but that logic doesn’t always hold true. I mean, if a turbo works, why isn’t it standard equipment on the Corvette? The car’s supposed to go fast, right? Wouldn’t GM have put a turbo on there if they knew it would make the car faster?

          • YouDidWhatNow? says:

            What you’re saying is that consumers shouldn’t be responsible for checking into a product before they buy it – you want to throw caveat emptor out the window.

            That is a horrific mistake.

            If we changed the way we assign that responsibility, to either the seller or the government, just think of the mayhem that would ensue. Or, to be more precise, sue. People could sue for anything they wanted to…and on the flipside, sellers would probably be afraid to make any claims for any products at all, for fear that someone wouldn’t be satisfied, and sue them.

            No, the onus must be on the consumer to actually do the diligence to verify that a product will meet their needs before they buy it…and verifying monumentally stupid assertions like this one should be among the easiest things you ever do as a consumer. There is no possible way, ever, that anything you plug into your cigarette lighter is going to save you gas.

            The problem is that people will believe what they want to believe, and they will frequently believe anything you tell them…and they will continue to believe them even after having been shown conclusive evidence that the assertions they are believing in are false.

            That phenomenon is why we have:
            Apple products
            Bose products
            Monster Cable products
            Astrology/Palm Reading/Mediums/etc.
            Nigeria email scams

            …so on and so forth.

            Now, it would seem to me that the best thing to do would be to actually regulate the associated industries in such a way as to make it difficult, if not impossible, to make unfounded claims. All forms of “alternative medicine” for example would have to undergo actual clinical trials to prove some kind of efficacy for some kind of ailment – just like actual medicine does. BTW, the only alternative to medicine is dying…but people still buy “Airborne” by the truckload.

            If Apple/Bose/Monster Cable want to make audacious claims about how their product is better than others, enforce a requirement of proof. And a requirement of adequate consumer comparison protections…which is to say, if Bose wants to sell their wildly overpriced and ridiculously under-capable audio products, force them to allow their products to be showcased and tested right along with all other audio products on the market…rather than refusing to let any credible reviews to be made of their products, or having “Bose-only” listening rooms in retail stores where you are unable to compare competing products in the same environment.

            If astrologers/mediums/whatever want to claim that they can do [all of the BS they claim they can do] have them undergo certification testing from a government board where they have to prove that they can see the future/talk to your dead mum/find your dog/etc. You have to have a state certificate to cut someone’s hair for crying out loud…if you’re claiming to be able to tell someone what the future holds, maybe you should be certified for that too.

            • vastrightwing says:

              Your point about Bose is good. They don’t allow retailers to compare products. Their marketing tact is to exploit our inability to remember differences in sound for more than very brief periods. There was a smart retailer who used to buy the latest Bose equipment and he set it up in his store so people could actually compare Bose to his competing offerings. It was an excellent strategy. Once people heard the Bose and then his stuff, they were amazed at how much better the less expensive stuff sounded.

              That’s not to say Bose doesn’t sound good, rather, that you’re way over paying for the quality you think you’re getting. But you don’t know that until you can compare.

            • Shadowfax says:

              I’m saying companies should be required to tell the truth about what they sell, and that they should be required to do so in non-misleading plain English. No more of this “up to 25% better fuel economy” when in reality every car will get 0% better fuel economy.

  10. Daverson says:

    It’s not really false advertising; the phrase “up to n” includes the value of 0.

  11. YouDidWhatNow? says:

    Fools. It’s electro-homeopathy with rare earth magnets that condition the holistic well-being of the oneness of you and your vehicle. Science can’t measure it because science doesn’t *believe*.

  12. APriusAndAGrill says:

    Thats it, Im gonna sell my fuel crystal idea.

  13. FireJayPa says:

    I’m sure the free market will sort this out. And anyway, the only people dumb enough to buy this are probably the same unwashed masses that buy things like lotto tickets.

    • palfas says:

      you are just full of love an joy aren’t you? Don’t forget you need all the “unwashed masses” to server you burgers and wash your fancy cars.

      Just because only stupid people buy it doesn’t make it okay for a company to sell it and make false claims about it.

  14. Back to waiting, but I did get a cute dragon ear cuff says:

    I have had many discussions with supposedly rational, intelligent people about the various “fuel saving” devices out there. It is amazing the number of people that fall for them. Back in 2005 I was getting a magazine for fleet managers that featured something similar. I had a back and forth with the editor who finally saw the light.

    My main argument, besides the very obvious snake oil and conspiracy claims was the following:

    Don’t you think that with the recent spike in fuel prices, that if something like this worked as advertised that the national media would be all over it? And with all the push for fuel economy, wouldn’t it make sense that if this product worked as advertised the automobile manufacturers would be installing them in all new vehicles? Increase the CAFE by up to 25% of our entire line for $59.99 per vehicle (assuming they pay retail for each one-how much of a discount would they get for a million units?)? You would see the manufacturers stumbling over themselves to get these into vehicles.

    That argument makes the supposedly intelligent people very sheepishly admit that either:

    A) they are being duped
    B) There is a vast conspiracy between the oil companies and ALL auto manufacturers.

    If B, where is Wikileaks when you need them

    • Nigerian prince looking for business partner says:

      Some of the fuel saving devices do work but there’s always a compromise. There are many kits out there that reprogram your vehicle’s OBC to tweak fuel mixtures, shut down cylinders, etc. at the expense of lost HP.

    • GuyGuidoEyesSteveDaveâ„¢ says:

      During last Easter/Thanksgiving, I had to deal with my Aunt’s neighbor who is a conspiracy theorist. He was extolling the virtue of adding acetone to your gas. I started believing him, until he broke out how a friend of his had a 300MPG carb and someone came into his driveway and stole it. That’s classic urban legend, so I really doubted much of what he said. What made me really care less what he said was when i asked why if adding a tiny amount of acetone made the fuel better/gave you more MPG/all for pennies of acetone, why doesn’t one of the gas companies add it for you automatically and then people would buy THAT companies gas. He had no answer.

  15. Consumer David says:

    F. U. China.

  16. Blueskylaw says:

    “Certified lab and field tests show increased MPG of up to 25%”

    They forgot to say: or as little as nothing.

    • Mr. Fix-It says: "Canadian Bacon is best bacon!" says:

      25% of zero is still zero. The math still adds up, which is why they can dodge false advertising. ;3

  17. sirjorge says:

    is it too much to ask for a “consumer” to read into and “KNOW” what they are buying? I guess so.

  18. sirwired says:

    I just love all the conspiracy theories about how the automakers and oil comapnies are in cahoots to make cars burn extra gas, surpress cars that run on water, hide fuel-saving things, etc.

    As if the world wouldn’t beat down the door of any automaker who could make a car that would run for free… That would be way more valuable than any bribe an oil company could come up with and successfully hide.

    • kc2idf says:

      I am annoyed by the inefficiency of vehicles, but a lot of this stems from the expectations we have of them, and has nothing to do with conspiracies. Largely, we, as a society, have done this to ourselves.

      More efficient vehicles can be built, but they are expensive (hybrids, anything by Tesla), or don’t look “right” (Smart, Mini Cooper) or aren’t fun to drive (Geo Metro) or some similar fault that, again, we, as a society, taken on the whole, won’t tolerate.

      There is an exception. The first time third time around with electric cars (the early 90’s), the cars lost out because the car makers didn’t want to make them. This, in turn, was because they were low-maintenance compared to ICE cars, and so there was not as good of a market in parts. I think the fourth time around (now), they might actually take hold.

  19. larrymac thinks testing should have occurred says:

    “Very positive affects” – so, like, Fuel Doctor is cheerful?

    Also, no SAG members were endangered during the filming of this video.

  20. crazydavythe1st says:

    Even if this did condition your car’s electrical systems, each device that is powered by your car’s electrical system already “conditions” the power if need be. Even if this device worked as intended, it wouldn’t save you a penny.

  21. wrbwrx says:

    Meh. My tornado fuel saver is way better.

  22. I wumbo. You wumbo. He- she- me... wumbo. Wumbo; Wumboing; We'll have thee wumbo; Wumborama; Wumbology; the study of Wumbo. says:

    “Very positive affects”? I can’t trust a company with incorrect word usage on their packaging.

    House power?!

    • GearheadGeek says:

      It’s probably intentional… [selling lots of these induces] a positive affect [in the owner of the company that makes them.] ;) They’ll say in court that you just THOUGHT they meant the verb form, they can’t be responsible for your misinterpretation.

  23. Winteridge2 says:

    P.T Barnum said it best.

  24. A.Mercer says:

    Has anyone gone to Amazon and read the comments on it?

    3 People gave it 5 stars (I wonder how much they were paid)
    1 Person gave it 4 stars (Probably did not pay that person enough)
    2 People gave it 1 star (The people who actually used it)

    • Jimmy60 says:

      They’re hilarious.

      I like this one: “I drive a Ford F150 SuperCrew with a 454 V8.”

      When did Ford make a 454? The 454 is a Chev motor that I think they stopped using in the mid 90’s.

  25. Jimmy60 says:

    Fuel saving devices can actually work. Only via placebo though. When a person installs one they have decided to get serious about saving fuel and the subconsciously adjust their driving habits and get better economy which they, in turn, credit to the device. If you install one of these into a car and the driver isn’t aware of it it will have no effect.

    The reality is no one knows more about squeezing economy out of an engine better than the engineers who design them.

    • partofme says:

      This could go 0.001 steps past placebo affect, actually. An earlier poster provided a link that breaks down the internals, showing that it is a simple high/low voltage indicator. If you but your vehicle in high-load situations, there will be a brief lag in generation, causing a small and brief decrease in voltage. If it happens to be just perfect for the performance of your alternator, it could trip the ‘doc’ to give you a red light. Then, it could possibly cause someone to put their car in fewer high-load situations, or to do it more slowly. Essentially, it would do the same thing (in a very reduced capacity) as the little leaf or whatever they’re putting in dashes now that try to convince you to drive economically… only it wouldn’t care about heavy breaking situations or a myriad of other low economy situations, just a very very brief high-load situation.

      • partofme says:

        It should be mentioned, if you’re wanting to check out the sweet sweet increase in house power, you’ll take 0.001 steps forward and 3 steps back.

  26. bruce9432 says:

    Reminds me of a spoof of J.C. Whitney catalog done by Car and Driver,

    ” Burmese Gas Snake. Put it in your tank and it will eat all the harmful red molecules”

  27. Big Mama Pain says:

    Maybe it’s a placebo effect. Knowing that it is there and blinking at you makes you more aware of your driving; we all know little ways to improve gas mileage (not speeding, not racing out of a stop, timing lights so you don’t idle, etc) but most do not follow it. They could have at least made it useful by adding a usb port in it or something, that way when you realize it’s a crock of shit, you still at least get something out of it.

  28. Hungry Dog says:

    If anyone is interested I have a small rock that will increase the mileage of your vehicles and it also keeps tigers away for only a mere 20 dollars.

    shipping not included.

  29. aydiosmio says:

    Here’s an electrical analysis of the device with schematics and photos. It’s really just pretty lights for your dash.

  30. Clyde Barrow says:

    I wonder how much money was made on this junk.

  31. duncanblackthorne says:


    People are SO gullible! There have been literally dozens of allegedly fuel-saving snake-oil devices and additives for internal combustion engines over the decades, and they never work, but people keep buying ’em..

  32. duncanblackthorne says:

    Additionally, here’s a complete analysis and schematic diagram of this “device”.
    It does NOTHING.

  33. commenterofsize says:

    While I’m very skeptical of any claim of a mileage booster, there’s probably a little bit more to the story. Non-disclosure: I don’t have anything to do with Fuel Doctor, I don’t own one, I advise much skepticism.

    The cars that Consumer Reports uses for mileage tests are probably maintained well. If a product claims to lower electrical noise on “the system,” we should not expect well-maintained cars to benefit as much. Fuel Doctor claims that their product works better on cars that are over 2 years old; only 2 of 10 cars that Consumer Reports used were that old.

    As to whether car manufacturers know about this, what do they care about the performance of a car several years down the line? It should surprise no one if a car’s electrical components degrade shortly after warranty periods end. Are we suddenly to believe that car manufacturers are paragons of quality and durability?

    I suspect this works by generating destructive interference to reduce noise. If a car’s electrical system were particularly noisy and if fuel injectors and such are affected by that noise, this isn’t such a far-fetched idea. I don’ know whether something you plug into the lighter socket can do anything about it, but I don’t know that it cannot, either.

    I call modest shenanigans on Consumer Reports for testing on newer well-maintained cars, when most of us drive older cars that we are too lazy to maintain. I also suspect a little bit of observer bias, because it looks like the test assumed that the product is bogus.

    • GuyGuidoEyesSteveDaveâ„¢ says:

      As to whether car manufacturers know about this, what do they care about the performance of a car several years down the line?

      Have you ever seen ads for car companies talking about re-sale prices for their older cars or how their cars hold their value longer?

      I suspect this works by generating destructive interference to reduce noise.

      Does it also increase the efficiency of the bussard collector in your air intake, which help replenish some of the hydrogen that is lost in the fuel filter?

  34. Nighthawke says:

    Hmm, I wonder if his landlord knows he’s working a business out of his apartment. Don’t they have rules against that sort of thing?

    I googled his address and the closest spot to the address was either a WuMu bank, a Baby’s R Us shop, a strip mall that might have a rent a PO box place, or a gated apartment complex; take your pick.

  35. mike says:

    Fuel Doctor is on Twitter. Let’s get ’em:

  36. donkeydonkeypublicbathroom says:

    sure, but how many gee bees does it have?

  37. Robert Nagel says:

    Not true!!! As an experiment I once added all of the devices I could find to my car and every 100 miles I had to stop and drain gas out of the tank to keep it from over flowing. You people are just too cynical.

  38. banmojo says:

    On the one hand, I want to say that this kind of advertising should TOTALLY be illegal – it’s so obviously untrue. On the OTHER hand, I want to say that IT’S SO FREAKIN’ OBVIOUSLY UNTRUE, so anyone who actually FALLS for this bs kinda deserves to get conned.


  39. KMFDM781 says:

    As a mechanic, it makes me sad that people will actually buy something like this.

  40. Fuel Doctor says:

    How many of the commenters have actually given FD-47 a chance to do what it claims to do? If you have, and FD-47 did not improve your older vehicle’s performance, you can always get a full refund with no shipping costs to you.

    As for Consumer Reports’ findings, Fuel Doctor has officially addressed that issue on the official site: