GREENVILLE, S.C. -- Can a gas-saving device being sold on the Internet actually double your fuel mileage, as the makers claim?

Water For Gas: Final Results

Three weeks ago, WYFF News 4's Tim Waller went in search of that answer by purchasing the "water4gas" system for $97. The system produces a mixture of hydrogen and oxygen, or "HHO," that the sellers claim drastically increases gas mileage.

To test that claim, Waller sought help from Greenville Tech's Center for Automotive Technology. Instructors agreed to build the device and install it on a 1990 Buick Century.

Early test results were encouraging.

"It works! We saw an instant change in how the car was running," Howard said earlier this month when the device was first installed. "The sensor values changed. I know for a fact fuel is being produced in this bottle."

As promised, the Mason jar filled with water and baking soda began to produce a hydrogen, and seemed to give the car an extra burst of energy. But officials said 2-3 weeks of road-testing would be required to see if the water4gas system increased mileage.

Now, three weeks later, the final test results are in.

"No. It did not improve mileage," said Sumner Huckaby, Dean of Greenville Tech's Center for Automotive Technology.

In fact, officials said they noticed a mileage decrease after installing the water4gas device.

" It dropped 2 miles per gallon," said automotive instructor Preston Howard.

The results are sure to disappoint thousands of News 4 viewers, who were hopeful the water4gas system would work.

In the past three weeks, News 4 has been inundated with emails from people looking to ease their pain at the pump.

"The system we built was the average Joe system. Very cheap. Very non-technical," said Howard.

Officials said the device "confused" the car's sensors, and caused it to burn more gas to compensate. They also said it worked the alternator harder, drawing enough juice to drain most batteries.

The way to correct these problems, according to the water4gas manual, is to install a potentiometer, which alters the vehicle's emissions.

Such an installation could be illegal, according to the Dean of Greenville Tech's Automotive Department.

"You're either adding hydrocarbons or carbon monoxide and other things to the atmosphere that we're trying to get rid of, and you're affecting the catalytic converter and its ability to work," said Huckaby.

Greenville Tech officials said they believe the idea of boosting gas-mileage with a hydrogen-producing device still holds merit.

"I think the concept is good, but it's going to take more money and more expertise than the average person has," said Huckaby. "What we did is not going to save the world, but I hope somebody out there does come up with some design that eventually gets us off of maybe oil entirely," said Howard.