Woman filling up her convertible's gas tank | BraunS/Getty Images

Dear Driving for Dollars,

Gas prices seem to keep going up in my area and driving my truck is just killing my budget, but I can’t afford a new car.

I noticed a bunch of different products in an auto parts store recently that are supposed to improve a car’s gas mileage, like stuff you add to the fuel or the oil, for example.

Which ones work?

— Juan Carlos

Dear Juan Carlos,

I’m sorry to report that it is unlikely that you will see any improvement in your car’s gas mileage by using any of these products. AAA’s Automotive Research Center has literally tested dozens of additives and devices that claim to improve fuel economy over the last 3 decades and has not found anything that works. (Fuel additives, lubricant additives and tablets that go into the fuel tank, for example, haven’t been shown to significantly improve vehicle mileage.)

Furthermore, these products must be tested by the Environmental Protection Agency, or EPA, and the state overseer (such as the California Air Resources Board) if there is one, before they can be legally sold. This does not mean they work.

In fact, these tests only require the manufacturer to prove that the products do not harm the car or increase its pollution emissions. In other words, they don’t have to prove that the product actually increases fuel economy.

If you drive an older car, it’s likely that there is a component that is not functioning properly, which is why it is reducing your fuel economy.

RATE SEARCH: If you’re in the market for a new car and want to compare car loans, check interest rates now at Bankrate.

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