Yahoo Autos 
Fuel-Saving Devices Debunked
Fuel's Gold: Too good to be true? Dynamic Ionizer, Fuel Doctor FD-47, and three others tested.
MORE AT car and driver
The key to any hustle is a believable story. It’s no different with fuel-saving flimflams, which often claim to exploit some small, overlooked factor that automakers or oil companies don’t want you to know about. Normally, we wouldn’t give a second thought to fuel-economy hucksterism, but our dedication to journalistic inquiry—and our desire to save you a few bucks in these times of rising gas prices—found us ordering five items that promise to stretch your petrodollar. Four of the five devices showed up, and we tested each in a Mazda 3 and a Jeep Grand Cherokee at steady speeds—35 and 70 mph—on the oval test track at Chrysler’s Chelsea proving ground. A ScanGauge II tool (www.scangauge.com), which plugs into a vehicle’s OBD II port, provided accurate average-fuel-economy measurements. The results? Well, we hope they don’t surprise you.
DYNAMIC IONIZER
$30.00 (www.toa-corp.co.jp)
The Claim: “Simply placed in the fuel tank or air filter, the Dynamic Ionizer pellets act as a molecular Ionizer on the fuel in the tank and air on the filter. This dynamic ionizing effect energies [sic] the fuel and air at molecular level [sic] causing [sic] to be agitated as it enters the combustion chambers.”
The Result: We never had a chance to try out these magic beans. Six weeks after we received a shipping notification from pre-tsunami Japan, this product had yet to arrive.
FUEL DOCTOR FD-47
$59.99 (www.fueldoctorusa.com)
The Claim: Plugged into the cigarette-lighter socket, “the FD-47 increases a vehicle’s miles per gallon (MPG) through power conditioning of the vehicle’s electrical systems. Conditioned and clean power allows the vehicle’s electronic control unit (ECU), fuel injection and engine timing equipment to operate more efficiently.”
The Result: The modest improvement we saw is nowhere near the claim of “up to 25 percent” more mpg and likely attributable to minor variables such as wind. Post-test, we cracked open the FD-47 to find a simple circuit board for the LED lights. Even if you could “condition” the ECU through the lighter socket, it’s unlikely the Fuel Doctor is doing so. On the upside, it might help prevent you from smoking in your car.
35 mph: +2% 70 mph: +1%
Update: The people at Fuel Doctor take issue with our test of their product. Fuel Doctor claims that its product is meant for vehicles that are 2 or more years old. We acknowledge that our test was performed on newer vehicles and stand behind our result. If you wish to perform your own examination we refer you to Fuel Doctor’s 90-day money back guarantee. We recommend you don't bother, though. Our follow-up test, performed with help from an independent expert, supports our initial conclusion.
