The costly mistake many drivers make when filling their car with gas is to overfill it by topping it off. When the gas pump nozzle clicks off, do you stop or do you keep pumping? Are you trying to add more gas your tank after the shutoff trying to stuff as much in as possible? Are you pumping more gas after the shutoff to round your total cost to the nearest full dollar amount? If either of these scenarios are true, or if any other reason causes you to top off your tank you have developed a bad habit that is costing you money and is contributing to air pollution.

Most gas stations are equipped with pumps that have vapor recovery systems to recover gas vapors keeping those vapors from getting into the air. If you top off your tank it will cause you to pay for gas that is drawn back into the gas station's vapor recovery system.

The extra gas you are trying pump may be drawn back through the vapor recovery system into the station's tanks. Then in essence you are paying for fuel that is not going into your tank but is going into the gas station's tanks. This, of course, raises your cost of gas.

When you overfill your gas tank it is almost a certainty that gasoline will evaporate or will be spilled. If either of these or both of these occur it means buying gas that is not getting into your car. That has to hurt you in the wallet.

There are more undesirable situations that can happen when overfilling your gas tank. Gas expands as it warms up. This is certainly something to keep in mind in the summer or in areas with warm weather. Gas in underground tanks will be cooler than the air as the ground insulates it from the heat. As the fuel in your tank gets warmer it expands. As the fuel expands it has to have more room.

If you overfill your car, there is no room for the fuel to expand. As the gas expands it has to go somewhere. It could easily find it's way into the vapor collection system of your own car. This may foul the vapor system causing it to malfunction.

The fuel that expands is lost gasoline that you have paid for. You paid for gas that you are not able to use. The result: your cost of gasoline goes up. But that is not the end of your increased costs! If the expanding fuel ends up in your car's vapor collection system it will negatively affect the system. If that occurs your vehicle will become much less efficient.

A vehicle that runs inefficiently burns more fuel which translates into spending more money on gas. That is a double hit in the wallet, once for the fuel that is lost directly and second for the additional gas your vehicle uses because it is running inefficiently.

Gas vapors add toxic substances such as benzene to the air. This is a major contributor to days that are designated ozone warning days. Fuel vapors are detrimental for your health and harmful to you if inhaled. When you overfill your tank you end up with vapors added to the air right where you are pumping. This will cause you to inhale toxic fumes.

The next time you stop to fill your vehicle, when the pump stops don't try to add any more gas, your tank should be quite full. Don't overfill it! Don't top it off! You will save yourself fuel and money but you will also contribute to preserving your good health and preserving the environment!