The claims for the Fuel Doctor FD-47 sound intriguing. Its packaging says it increases power and reduces emissions, and that “field tests show up to 25% more M.P.G.” The company’s website says it achieves that “through power conditioning of the vehicle’s electrical systems” and by preventing electrical interference. A TV commercial claims that this “fuel-efficiency booster draws that interference, filters it, then sends back a more stable current.” And all you have to do is plug it into a car’s 12-volt power outlet. So why didn’t Ford or GM think of that?
The answer: Because it doesn’t work. 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.
We tested two samples of the FD-47 on 10 vehicles, with different types of engines, including four-cylinder models, standard and turbocharged V6s, and gas and turbodiesel-powered V8s. We ran each vehicle through our standard series of acceleration and fuel-economy tests, and the results were virtually the same with or without the device. The company says that the Fuel Doctor is recommended for use on vehicles 24 months old and older but that positive effects can be expected on many newer vehicles as well. Two of our test vehicles were older than 24 months.
In the past, we’ve tested bolt-on devices that were claimed to provide big fueleconomy and performance improvements, including the Fuel Genie, Platinum Gas Saver, and Tornado Fuel Saver. But we have yet to find one that makes a significant difference. And we’re not alone in disputing those products’ claims. The Environmental Protection Agency’s website (www.epa.gov/otaq/consumer/reports.htm) lists scores of such devices that it has tested with similar results.
Bottom line. Save your money. We have judged the Fuel Doctor FD-47 to be a Don’t Buy: Performance Problem. You could fill up your tank with what you would have spent on it.
See our guide to fuel economy for advice on saving gasoline. Learn about future technologies in our guide to alternative fuels.
Related: New Fuel Doctor tests: Still no MPG magic