With gas prices headed toward $5 a gallon, many people are understandably looking for ways to cut costs at the pump--and some sites can help you hunt down the lowest gas price in your neighborhood. But the Web (not to mention your inbox) is also brimming with dubious offers for free gas and schemes to save at the pump. Experts say that in most cases, you should steer clear.

"It comes down to your mother's advice," says John Paul, spokesperson for the Automobile Association of America, "If it sounds too good to be true, it probably is."

But the Better Business Bureau reports that, as gas prices have gone up, so have complaints about sites--some of them heavily promoted in search-engine ads--that promise free gas but deliver only headaches and unwanted e-mail.

'Fill 'er Up With Evian'

The most prevalent gas-savings pitch I've seen on the Web lately is for a kit that's supposed to show how to use water to supplement a car's use of gasoline in order to reduce fuel costs. A headline on a site called Half Water Half Gas, for example, reads: "Use water as fuel, cut your costs by as much as 60 percent and make the environment better and make your car run better at the same time."

Most of these water-as-fuel kits show you how to create a Mason jar-size gizmo that sits under your car's hood and, supposedly, extracts hydrogen from water. According to Half Water Half Gas, the hydrogen then is mixed with oxygen to create a fuel called HHO (or oxyhydrogen), which the device then pumps into your engine's intake manifold to reduce (but not eliminate) its dependence on gas.

Sites such as RunYourCarWithWater.com are also pitching $50 manuals for HHO conversion and conversion kits that range in price from $150 to $1150.

Experts say such car kits are hogwash. "All of these devices look like they could probably work for you, but let me tell you they don't," says AAA spokesperson Paul.