Ask Lauren Fix: Gasoline Myths!

Ask Lauren: Gasoline Myths!


Q:  “When filling up your gasoline tank I heard a percentage of the fuel is “lost” because of temperature changes, evaporation, leakage or issue of tank gauge calibration.  What is the truth?

A:  “Millions of dollars worth of gasoline is wasted every day by motorists, and neglecting vehicle maintenance is the culprit,” said Lauren Fix, The Car Coach and spokesperson for the Car Care Council. “Loose or missing gas caps, under-inflated tires, worn spark plugs and dirty air filters all contribute to poor fuel economy.”

Of these, one of the greatest culprits of gasoline “loss” are vehicle gas caps – About 17 percent of the vehicles on the roads have gas caps that are either damaged, loose or are missing altogether, causing 147 million gallons of gas to vaporize every year.

Q: Do you get more energy for your buck when you buy gas in winter?

A: Yes, unless you live somewhere that’s hot year-round.

Another variable to consider in gasoline loss is the effect of temperature changes. Just like other fluids, gasoline expands as it warms up. But gas pumps always dispense the same volume, both in winter’s chill and summer’s heat. So in warmer months, the fuel in your tank is less dense and packs less energy than in cold weather.  In the United States, the oil industry adjusts for temperature throughout its supply chain as gasoline is piped from refineries to distribution centers and trucked to gas stations. Only at the final step – the driver buying gas – is no adjustment made.  The industry, so far, has blocked efforts to bring temperature-adjusting pumps to the United States.

The issue hinges not just on physics but on the definition of a gallon. The oil industry considers a gallon of gas to be 231 cubic inches at 60 degrees. But fuel temperatures can change substantially with the seasons. And in warm-weather states, they often stay well above that level, meaning drivers usually get less energy in their tanks than they should.

Q: Is it better to fill up in the morning or at night than during the day?

A:  There are also plenty of gasoline myths to expose, one of which is the exaggerated importance of the day of day you fill up your tank. It probably doesn’t make much difference. Although gasoline expands in warmer temperatures, modern underground storage tanks hold temperatures quite well. As a result, the fuel tends to stay near whatever temperature it had when it was delivered to the station.

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