Recent unstable gasoline prices have pushed some car owners to make modification to their vehicles that purportedly increase gas mileage and engine performance.

An automotive association, though, urges caution when tinkering with an often valuable investment.

For the past five years, Bluffdale resident Jared Peterson has been operating his SUV with the help of a self-contained hydrogen gas device called the Hydro Capacitor, which he built himself. Peterson continues to re-invent the module and has installed it in more than a dozen vehicles, whose owners report better gas mileage over time.

"I was fed up with gas prices going through the roof," he said. "If it's a burden to me, it's probably a burden to everyone else."

Benefits of his invention, Peterson said, include increased power to the vehicle, cleaner exhaust and a cooler and quieter engine, "not to mention a better fuel economy."

The mechanically drafted cylindric contraption made of Plexi-glass, metal gaskets and tubing mounts in any vehicle and "supplies a hydrogen fuel/gas to the engine, allowing the engine to run more efficiently," Peterson said. The vehicle, he said, then runs on "more efficient vapor gas rather than liquid gasoline."

"Most have seen anywhere from a 25 percent to a 75 percent increase in fuel economy," he said. "Results vary depending on vehicle size and model, but many have their money back in only a few months."

For a semi-truck, Peterson said, mileage can increase as much as two miles per gallon, which works out to a 50 percent to 65 percent increase. He said a friend's small passenger car has seen a 10- to 15-mile per gallon increase in gas mileage.

However, AAA Utah spokeswoman Roylane Fairclough said the prospect of better mileage may not be worth the risk for people whose vehicle is their second most expensive investment ever.

"We don't know the specifics, but we do know that these things can be harmful to your vehicle," she said.

Drivers, she said, are better off using known gas-saving measures such as maintaining optimum tire pressure, smoother driving and carrying a lighter load.

"It just doesn't make sense to make those kinds of changes when we don't really know the outcomes," Fairclough said.

But Peterson is determined to help people save money and in turn preserve the environment with what he says is a cleaner hydrogen gas that chemically puts off more oxygen.

Word of mouth generated enough interest in his device that he quit his day job as a mortgage broker/financial planner five months ago to meet the demand for Hydro Capacitors.