NORTH TEXAS (CBSDFW.COM) – For the first time since October of 2008, the average price of gas is now about $3.50 a gallon in every major city in Texas. As the price of gas goes up, North Texans are seeing more ads claiming to boost your cars gas mileage.

Officials with the Texas Better Business Bureau (BBB) say all of the ads have been tested and all of them are scams.

“It’s another money making device that people have come up with. And you can send away for it, you can stop at different stores and pick it up,” explained Kristi Pena with the BBB.

Pena says several of the products actually increase exhaust emissions, and some of them could damage your engine.

The basic advice from the Federal Trade Commission (FTC) and the BBB is ‘if it seems too good to be true, it probably is’.

Should you still want to give any product a try, the BBB and FTC have a few suggestions:

• If a company claims it has an endorsement from government, it’s a lie. The EPA has issued reports based on its testing and evaluation of some products. The agency has posted on its website a list of approved gas additives.

• Be leery of customer testimonials. Few people have the ability or the equipment to test for precise changes in gas mileage.

• Be skeptical that a single product can achieve double-digit savings in your fuel economy.

• Check with a mechanic or professional before installing or using a product.

There are steps consumers can take to increase fuel efficiency and get the most out of a tank of gas. The BBB suggests:

• Driving more efficiently. Stay within posted speed limits. Gas mileage decreases rapidly at speeds above 60 miles per hour.

• Avoid “jackrabbit” starts and stops. Accelerate slowly when starting from a dead stop. Don’t push the pedal down more than one-quarter of the way; this allows the carburetor to function at peak efficiency.

• Use overdrive gears and cruise controls when appropriate. They improve the fuel economy of your car when driving on a highway.

• Keep windows closed when traveling at highway speeds. Open windows cause air drag, reducing your mileage by 10 percent.

• Avoid rough roads whenever possible. Dirt or gravel can rob you of up to 30 percent of your gas mileage.

• Remove excess weight from the trunk. An extra 100 pounds can reduce a typical car’s fuel economy by up to two percent.

• Properly maintain your car. Keep the engine tuned, tires inflated and aligned, change the oil on schedule, and check and replace air filters regularly. Replacing clogged filters can increase gas mileage up to 10 percent.

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