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Can copper tubing, cheap magnets and wacky gimmicks really boost your mileage by as much as 300 percent? PM’s Mike Allen puts the latest MPG gadgets to the test. Please step back from the truck.

Aug 25, 2005 As long as there have been cars, there have been gadgets that promise revolutionary improvements in performance and mileage. And every time there’s a spike in fuel prices, these gadgets proliferate like mushrooms after a spring rain. Like now, with crude oil over $60 per barrel. Scan the Internet, store shelves and, yes, even the classified ads in the back of PM, and you will find dozens of devices promising to boost power, reduce emissions and, of course, improve mileage by 20, 40, even 300 percent!

Hey, we’re not gullible. But we’re not close-minded either. Could it be that the basement tinkerers behind most of these products have stumbled upon some heretofore undiscovered principle of physics or thermodynamics? Is it possible that the major auto companies have overlooked–or deliberately avoided–simple engine modifications that would give their cars and trucks an overwhelming advantage in the marketplace? Instead of dismissing such far-fetched notions out of hand, we decided to give the gas-gadget makers a chance to prove their miraculous claims.

We purchased seven typical gadgets–ranging in price from $20 to nearly $400–representing the most common approaches used by devices claiming to boost mileage, such as applying magnets to the fuel line, modifying air intakes or injecting extra fuel into the engine.

We conducted our tests at the Universal Technical Institute, a large training facility for automotive technicians, in Houston. We chose four full-size pickup trucks from UTI’s fleet as our test vehicles. Why pickups? Well, for one thing, the pickup truck tends to be the poster child for conspicuous consumption of Mideast oil. Also, truck engine compartments are roomy enough that we could install the products without feeling like we were assembling a ship in a bottle.

We strapped the trucks down to a pair of chassis dynamometers and ran them dry of gasoline. Then we added a measured quantity of gas, and ran four dyno pulls to determine horsepower and torque. Next, we accelerated to a corrected 70 mph, set the cruise control to keep the speeds consistent and ran the trucks dry again. This gave us a base line of each truck’s unmodified power and fuel consumption.

We gassed up the trucks, installed our gas-savers and repeated the tests. (We didn’t check for emissions, figuring most people who buy these products are fighting a holding action on their wallets, not on the environment.) Here are the gadgets and how they performed.

FuelSaver and Fuel Optimiser


There are dozens of fuel-line magnets on the market. We tested two. They all make similar claims: substantial improvements in fuel economy, reduced emissions and increased horsepower.

According to the people selling these devices, as gasoline flows past the magnet, the magnetic field will “break apart clusters of fuel molecules so gas burns more efficiently.” Problem: Gasoline molecules aren’t magnetic, not at all. But wait, there’s more. If the fuel line is steel, as many are, the lines of magnetic flux will follow the fuel-line walls instead of passing through the fuel.

THE DYNO SAYS: As we suspected, neither device had any significant effect on performance or economy.



These devices, which are usually installed on the upstream side of the mass airflow (MAF) sensor, use stationary vanes or, on some devices, spinning blades to make the inlet air between the air cleaner and intake manifold whirl around in a mini-tornado. This vortex supposedly mixes fuel more thoroughly with air, which means the fuel will, theoretically, burn more completely in the combustion chamber. Trouble is, there’s a lot of intake tract downstream from these devices designed to maximize a smooth airflow. Turbulence, coupled with the restricted airflow caused by the device, can only reduce the amount of air sucked into the manifold. Less air means less power.

Again, we tested two devices. The TornadoFuelSaver is a nicely made stainless steel contraption, available in an assortment of sizes to fit most vehicles. We installed it on our truck’s intake tract immediately upstream of the MAF sensor. We purchased the second device, the Intake Twister, on eBay. It was crudely handmade from sheet-aluminum flashing and pop rivets. It looked like something we could make in about 10 minutes from an old soda can. The staff at UTI was reluctant to install it: The bent sheetmetal vanes looked as if they might break off and be digested by the engine. The device is one-size-fits-all, and is simply bent into a curl to insert it into the intake duct.

THE DYNO SAYS: Both devices reduced peak horsepower by more than 10 percent. The Intake Twister increased fuel consumption by about 20 percent; the TornadoFuelSaver provided no significant change.

Electronic Engine Ionizer Fuel Saver


The Electronic Engine Ionizer Fuel Saver consists of a couple of pieces of wire molded to some rubber blocks, which the manufacturer refers to as “capacitor blocks.” There are no capacitors in them, however, as we found out during the test. The rubber blocks clip onto the spark plug wires near the plugs, and are intended to carry the “corona charge” from one cylinder’s plug wire to the electrodes of the other plugs. This charge is supposed to “cause a partial breakdown in the larger hydrocarbon molecules in all the non-firing cylinders, resulting in increased combustion efficiency.” Yeah. Normally, we try to prevent cross-coupling between spark plug wires to prevent crossfiring between cylinders. The Engine Ionizer seems calculated to promote crossfire.

THE DYNO SAYS: The truck we tested showed about a 15-hp loss with the Ionizer. About 10 miles into our economy test, the left bank of rubber capacitor blocks started to melt and sag onto the red-hot exhaust manifold. When smoke started to fill the dyno room, we interrupted the test and redressed the wires and capacitor blocks more securely. But when one on the right bank liquefied and dripped onto the manifold, we had flames a good 2 ft. tall, requiring the use of a 20-pound fire extinguisher. This, of course, terminated the test. Besides, most of the capacitor blocks looked like yesterday’s chewing gum. Consequently, we have no comment as to the abilities of the Electronic Engine Ionizer Fuel Saver to reduce fuel consumption.

Fuel Atomizer 2000


These devices take raw fuel and convert it to fuel vapor outside the engine, generally metering the fuel back into the engine through the PCV vacuum line. The advantage is supposed to be complete atomization of the fuel to its vapor phase. Fuel injected directly into the intake runners through a fuel injector is supposedly less available for combustion, because at least some of the fuel droplets are still liquid and liquid fuel doesn’t burn.

Where to start? The distribution of fuel through the customary vacuum tap used–the crankcase vent–may not necessarily meter the vaporized fuel equally to all cylinders. Those closer to the connection may get more fuel than those farther away, causing these cylinders to run rich. And even in the best-case scenario of equal distribution, the fuel-injection management computer checks the amount of oxygen in the exhaust and quickly leans the engine back to proper stoichiometric fuel/air mixture ratios. So, any amount of vaporized fuel the device allows in would simply be subtracted from the amount the computer normally dispenses.

We tested the Fuel Atomizer 2000, which takes fuel from the fuel rail and carries it via a length of copper tubing to the device, where it is mixed with air and sucked into the manifold through the PCV line as vapor.

THE DYNO SAYS: Theory predicted that there would be no change in power, because at high throttle settings the lowered intake manifold vacuum would simply not pull much–if any–fuel through the device. As expected, horsepower was not significantly changed; fuel economy was unchanged.



This technology was developed during World War II to provide emergency sprint power for turbosupercharged fighter planes. At altitude, there is less air for cooling engines. The turbos, however, cram air into the inlet at manifold pressures nearly the same as those at sea level. The compressed intake air, heated as it goes through the turbos, makes the engine even hotter. Spraying water, or a water-alcohol mixture, directly into the intake lowers the combustion-chamber temperatures. This permits substantially more power for brief periods. Several manufacturers have attempted to apply this technology to automotive use. We ordered an AquaTune from a classified ad in the back pages of PM. “AquaTune is like no other water injection system in that it is, in actuality, a fuel cell hydrogen processor. It produces hydrogen-rich bubbles before being introduced into the engine draft.” An “ultra-sonic barometric pressure chamber giving off ultra-sonic frequencies” apparently splits water molecules to create hydrogen bubbles. Anyone who can explain that, please call me–I’d like to make some hydrogen ultrasonically from water and solve the energy crisis while simultaneously eliminating global warming.

It was relatively easy to install the AquaTune, although we did need a few feet of our own vacuum line. (What do you want for $399?) Unlike the pump-fed water-injection systems on P-38 fighters, the AquaTune relies on intake manifold vacuum to pull distilled water from a plastic bottle and into the manifold. So, at periods of wide-open throttle, virtually no water should enter the engine.

THE DYNO SAYS: With the AquaTune adjusted according to the instructions, the test truck gave us 20 fewer horsepower and about a 20 percent poorer fuel economy.


We’ve tested nowhere near all of the fuel-saver gadgets on the market, and I’m sure purveyors of others will be waiting in our lobby soon. But not one of the items we tested worked. At all. There’s no ignoring the laws of physics, people. Your vehicle already burns over 99 percent of the fuel you pay for. Less than 1 percent is squandered as partially burned hydrocarbons and carbon monoxide before the exhaust hits the catalytic converter for the last laundering. Even if one of these miracle gadgets could make the combustion process 100 percent complete, the improvement in mileage resulting would be 1 percent. Any device that claims quantum-level increases needs to be examined with considerable skepticism.

We say caveat emptor (let the buyer beware). But there are plenty of people out there who say: “There’s one born every minute.” Prediction: Within a few weeks after the appearance of this article, there will be gas-saving gadgets on the market that tout themselves as “Featured in Popular Mechanics.” Someone will buy them. Probably not you.

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