Dozens of companies around the world will sell you devices claiming to improve your gas mileage.

For what seems like a nominal amount, the magic devices can apparently increase your fuel economy by double-digit percentage figures.

It seems too good to be true. And all too frequently, as Jalopnik has found out, it IS too good to be true.

Back in December they tested a product called the Fuelshark.

Fuelshark claims to save you ten percent or more on gas, by simply plugging the $39.95 device into your cigarette lighter.

The strange alienesque device glows blue, and according to the company, uses a capacitor to "stabilize your car's electrical system". By doing so it supposedly reduces load on the car's electrical system, and as we know, less electrical load means better fuel efficiency.

Only the Fuelshark doesn't do that. We can't use the word Jalopnik used to describe it, but it turns out the Fuelshark is big, steaming piles of that particular word.

In a reasonably scientific test the car used similar amounts of fuel whether fitted with the Fuelshark or not. Actually, it used a little more, but well within the scope of variability. It's this variability Fuelshark plays on to make its claims--it even says the best results will happen under variable driving conditions.

If the average customer finds they suddenly get 5 mpg more on their commute for a couple of days, they may put it down to the blue-glowing doorknob rather than the variability of traffic conditions. If they don't get instant results, they may assume Fuelshark's recommended variable driving conditions are to blame.

Either way, the capacitor inside the device has nowhere near enough power to do what the company says it will. Jalopnik notes that the capacitor can store about 120,000th the charge of the supercapacitor in the Mazda 6 with i-ELOOP technology.

In other words, it has enough capacity to keep the little blue LED lit for a few seconds. And not enough to reduce load on the electrical system. And therefore, not enough to save fuel.

The company exercised its right to reply, and included a few uninformative graphs along the way. This was also debunked.

Essentially, Fuelshark can be mentally filed away with those ten-buck magnet sets on eBay that claim to align the molecules in your fuel on the list of "things that do nothing for your gas mileage".

And at least the ten-buck magnet sets only cost ten bucks. As placebos go, you may as well pick one that's cheap.

Or if you really want to save gas, just drive a little better. Anticipate traffic, slow down a little and drive a little smoother. You'll get real, consistent results, and it won't have cost you a penny...


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