Savings claims may range anywhere from 12 to 25 percent. However, the EPA has evaluated or tested more than one hundred alleged gas-saving devices and found only a few that improve mileage and none that do so significantly. The gas-saving products on the market seem to fall into clearly defined categories. Although the EPA has not tested or evaluated every product, it has tried to examine at least one product in each category. See the list at the end of this brochure for category descriptions and product names.
Many ads feature glowing testimonials by satisfied customers.
Yet, few consumers have the ability or the equipment to test for precise changes in gas mileage after installing a gas-saving product. There are too many variables that affect fuel consumption, such as traffic, road and weather conditions, as well as the car's condition.