What are MPG caps?

Answer by  tigerlily787 (33)

An MPG cap is a gas-saving product to be added to a vehicle's fuel tank. According to Wiki Answers, they decrease emissions and pollution by 75 percent or more, and semi-trucks were saving almost 2 miles per gallon of diesel fuel. They help semi-truckers save hundreds of dollars per month and save the environment, too.

Answer by  donfran (32)

MPG caps are pellets that you drop into your gas tank when you fill up. They are supposed to create a coating in the combustion chamber of your engine that allows your fuel to burn more efficiently.

Answer by  superrosesmom (52)

MPG Caps are an accessory added to the car to help save on gas mileage. They do not work effectively.