Save Money and the Planet: Don't top off your gas tank

As the daughter of a truck driver, motorcycle enthusiast, and a born mechanic, I was told at age fifteen to never top off my gas tank. I didn’t question my father, but nearly twenty years later I still adhere to his words, which are now backed up by the EPA, car manufacturers, and local governments throughout the country. As an Oregon resident I can no longer pump my own gas and I have to be on top of the gas station attendants, for whom it seems policy to ask to top off.

On a recent road trip through California I noticed a little sticker on the gas pump that said, “Don’t top off”. The sticker then explained how it was bad for your wallet and bad for the environment. I wondered if Oregon had those same stickers. After a call to a local gas station, it seems they do not. The gentleman who gave me a few minutes of his time informed me that what the EPA had to say was a “crock” and that sometimes he could get an extra two gallons of gas into a tank after the nozzle clicked off. This statement inspired me to do some research into the air quality and carbon emissions for the state of Oregon and how topping off might be related.

In 2006 officials discovered that Oregon gas contains incredibly high levels of benzene (a carcinogen that has been linked to leukemia & cancer), higher than the national average. This is because refineries in the Northwest rely on crude oil from Alaska that is naturally high in benzene. Most Northwest refineries do not have the equipment to remove benzene when producing the gasoline we use, as the refineries were not required in the 1990’s to update their plants. Back then the air quality was pretty good. That’s not so true any more.

The Clean Air Act and Amendments of 1990 define a nonattainment area as a locality where air pollution levels persistently exceed National Ambient Air Quality Standards, or that contributes to ambient air quality in a nearby area that fails to meet standards. Designating an area as nonattainment is a formal rulemaking process, and EPA normally takes this action only after air quality standards have been exceeded for several consecutive years. Grants Pass ranks on the EPA’s list of “nonattainment areas” as does Medford and Eugene. Our carbon emissions are among the worst in the country. This is due to more than people just topping off their tanks, but it is a large part of the problem.

Topping off causes vapors and spillage. The state of Oregon only requires vapor recovery systems in Portland, Eugene/Springfield and Medford/Ashland. Think about all the gas stations out side of those regions adding an extra “gallon or two” to hundreds of tanks per week. There is bound to be some spillage and escaping vapors. This is detrimental when you consider that a shot glass (one ounce) of gasoline produces the same volatile organic compound emissions as a car driving 56 miles.

Reduce the impact of our fuel addicted lifestyles, next time they ask if you want to top off, “Just say no”.

The following information was provided by the EPA’s website.

Topping off the gas tank can result in your paying for gasoline that is fed back into the stations tanks because your gas tank is full. The gas nozzle automatically clicks off when your gas tank is full. In areas of ozone nonattainment, gas station pumps are equipped with vapor recovery systems that feed back gas vapors into their tanks to prevent vapors from escaping into the air and contributing to air pollution. Any additional gas you try to pump into your tank may be drawn into the vapor line and fed back into the station’s storage tanks.

Gasoline vapors are harmful to breathe. Gasoline vapors contribute to bad ozone days and are a source of toxic air pollutants such as benzene. Evaporation from the spillage of gas from overfilling can occur, contributing to the air pollution problem. Remember you pay for the gas that evaporates or is spilled on the ground.

You need extra room in your gas tank to allow the gasoline to expand. If you top off your tank, the extra gas may evaporate into your vehicle’s vapor collection system. That system may become fouled and will not work properly causing your vehicle to run poorly and have high gas emissions.

Topping off your gas tank may foul the stations vapor recovery system. Adding more gas after the nozzle has automatically shut off can cause the stations vapor recovery system to operate improperly. This contributes to the air pollution problem and may cause the gas pump to fail to work for the next person.

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Comments 2 comments

MoniqueAttinger profile image

MoniqueAttinger 7 years ago from Georgetown, ON

Very interesting! Thanks for the clear explanation of how topping off could not just cost me money but also cause more gas vapour to escape into the atmosphere.

someonewhoknows profile image

someonewhoknows 7 years ago from south and west of canada,north of ohio

Excellent research very informative.I thought everyone served themselves at gas stations these days.I remember when they had service station attendants where I live ,but that was in the 60's.Ithink they stopped the practice here in the early 70's.

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