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 tank there is a good chance that gasoline will evaporate or will be spilled.  Both of these costs you money for gas that is not getting into your car. That is not good for your 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 top off your tank, there is no room for the gasoline to expand.  What then happens to the expanding gas? It might find it’s way into the vapor collection system of your vehicle. This will easily foul the system causing it to work poorly.

The gasoline that expands and is lost is gasoline that you spent your money on. That means that again, you spent money for gas that you are not able to use. As a result your cost of gasoline is increased.  But you are not through loosing money!  If the expanding gas finds it’s way into your vapor collection system it could easily foul that system.  If that happens your car will operate very inefficiently.

A car that runs inefficiently means that you will use more gasoline  which means you will spend more money on gas. Thus you are hit doubly in the wallet, once for the gas that you loose directly and second for the extra fuel your car burns because it runs inefficiently. Ouch and 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.

When you next fill your truck or car, when the pump automatically stops don’t add any more fuel, your tank should be full enough. Don’t top it off, don’t overfill it. Not only will you be saving money but also helping your own health and helping the environment!