A mistake that many drivers make when filling their gas tank is to overfill it by topping it off. When the gas pump nozzle clicks off automatically,do you keep pumping? Are you trying to add as much gas as you can possibly stuff into your tank? Do you pump more gas after the automatic shutoff to round your total to nearest full dollar amount? In either case this is a bad habit that is most likely costing you a lot of money and is contributing to air pollution.

In many areas, a gas station's pumps have vapor recovery systems that recover gas vapors to keep those vapors from getting into the air. If you top off your gas tank it will result in you paying for gas that is drawn back into the gas station's vapor recovery system.

The extra gas you are trying to stuff into your tank may be drawn into the vapor recovery system back into the station's tanks. In that case you are paying for gas that is not going into your car but is going back into the gas station's tanks. The effect of this, of course, is to raise 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 bad things that can happen when topping off your gas tank. Gasoline expands as it gets warmer. This is certainly important in the summer or in climates with warm weather. Gas in the station's underground tanks will be cooler than the air. As the gas in your tank warms up it expands. As the gasoline expands it needs 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 gas that expands and is lost is gas that you have paid for. Again that means that you are paying for gas that you can't use. Your cost of gas is increased again. But that's not all that will happen. If the expanding gas fouls up the vapor collection system your car will operate less efficiently.

A less efficient car means less fuel efficiency which means you will use more gas which means it will cost you more money. The result is you are hit double in the wallet, once for the gas that is lost directly and second for the extra gas your car starts to burn because it is running inefficiently. Double ouch!!

Gas vapors are a major factor in adding toxic pollutants such as benzene to the air. This contributes to bad ozone days. Gas vapors are bad for your health and harmful to breathe. When you top off your tank you will end up with vapors released into the air. When this happens you are breathing in 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!