Don't get burned trying to stretch your gas mileage

Products don't make much difference, feds say, and some may harm the environment

If you're fuming about gas prices as you fuel up to hit the road for a summer getaway, think twice before pouring something in your tank or installing something on your engine that promises to improve your fuel efficiency.

Chances are it won't make much difference, if any, in your vehicle's performance. And it actually could hurt your car.

"Even though gas prices go up in the summer, the Environmental Protection Agency has not found any product that significantly improves gas mileage, and some could damage a car's engine or increase exhaust emissions," the Federal Trade Commission said last month in naming gas additives one of the top summer scams and frauds.

The agency suggests taking a skeptical look at products that claim they'll improve gas mileage. It says ads for these products seem to be more prevalent at times when gas prices are high — as they are now — but warns the savings are small even for the few products that have been found to work.

Claims that should make you put on the brakes include supposed endorsements from the federal government and promises that your fuel economy will rise by a specific percentage or number of miles per gallon.

The EPA requires fuel additives to be registered but it doesn't endorse them or test them for engine efficiency, emissions benefits or safety. Manufacturers are required only to report the chemical composition along with information about certain technical, marketing and health effects.

A list of registered additives is available at http://www.epa.gov (search for "list of registered fuel and fuel additives").

The registration process does not include checking the product's claims, meaning the EPA doesn't determine whether the fuel additive works as advertised.

"Do not assume that because a fuel additive has been registered with EPA that this implies anything about the safety, benefits, or claims made by the manufacturer," the EPA warns on its website.

The same goes for gadgets you can install on your car's engine, emission system, fuel system or exhaust system.

The FTC says the EPA has evaluated or tested more than 100 "alleged gas-saving devices" and "has not found any product that significantly improves gas mileage."

Marketers of those products may apply for EPA testing, but very few have done so in the past decade. Those test reports also are available at http://www.epa.gov (search for "aftermarket retrofit device evaluation program").

If a device isn't listed, that means the EPA has no information about the impact it will have on your vehicle. Some additives also have been tested through that program.

The most recent test was done in 2005. I can only presume marketers aren't lining up to have their devices tested because those that already have gone through the program generally didn't fare well.

The EPA says most devices it tested "had a neutral or negative effect on fuel economy and/or exhaust emissions."

That doesn't mean they're all worthless, though.

Tests in 1999 on PetroMoly HP Motor Oil showed a 3 percent improvement in highway fuel economy and 2 percent improvement in city fuel economy, which the EPA says were "statistically significant improvements for testing a single vehicle."

The EPA warns to be suspicious of several specific types of devices, including those that turn water into fuel.

"There are many advertisements about using the energy from your car's battery to split water molecules into hydrogen and oxygen gas which is then burned with your fuel. EPA has received no credible and complete data showing a positive fuel economy benefit from these devices."

It warns that the installation instructions for some equipment call for adjustments that would be considered "tampering" with a vehicle's emissions control system, something that's prohibited under the Clean Air Act and punishable by a fine.

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