Should You Buy Your Gas in the Morning?

One of the "gas mileage" tips going around lately is to buy your gas early in the morning as it contracts when it is cold, so you'll get "more" gas in the morning than in the afternoon when it is warm.

BALONEY!

In the first place, the underground tanks keep gas at a fairly constant temperature (around 60 degrees), so the biggest temperature variation in the gas you purchase is going to be controlled by when it was delivered to your gas station and by how long it was sitting in the tanker truck out in the sun. A good friend of mine (who has more time than I do) decided to see how much of a difference it really makes, anyway.

He got a glass laboratory vial, carefully marked for measurements on the side. He then filled it with a measured amount of fuel and capped it with a balloon to eliminate evaporation. He recorded the volume at room temperature and stuck it in the freezer. He measured the volume change at 17°F. Then he baked it in the sun to get it to 90°F. The change in volume from the lowest to the highest was only a 3% difference. Since it wasn’t likely the temperature would vary that drastically at the pump, we are able to conclude that that tip was baloney. It didn’t make that much difference what the temperature of the gas was. You’d still pretty much get a gallon when you pumped a gallon.

It seems like the best gas mileage improvements are still due to better driving habits.