Fuel Economy Tip – Fill Up in the Morning

Today’s tip will help you save a little bit each time you fill up, especially during the hot summer months.

Fill up early in the morning, when the day’s temperature is at its lowest.

I came across an interesting article that goes in depth regarding how “hot fuel” can end up costing you lots of money over time:

“As a liquid, gasoline expands and contracts depending on temperature. At the 60-degree standard, the 231-cubic-inch American gallon puts out a certain amount of energy. But that same amount of gas expands to more than 235 cubic inches at 90 degrees, even though consumers still only get 231 cubic inches at the pump.”

The 60-degree standard that is referenced in the above quote refers to the highest temperature at which gasoline should be sold, as stipulated by the U.S. government, and apparently is something that most people are unaware of.  I know I had no idea about the standard until I read the referenced article.

Unfortunately, this is hard to enforce and most gas is sold at a much higher temperature than 60 degrees – meaning you’re paying for gas that you’re not even getting.

So what does this mean for you, the consumer?

It means that in order for you to get the most gas for your money, you should try and fill up your car in the morning, when the air temperature is the coolest AND the gasoline temperature has had enough time to drop over night.

While the savings may not amount to much each time you fill up, over time you should start to see a difference.


  1. Thanks for the interesting article. I am happy to say that I learned something new today!

  2. Brian Carr says:

    Glad to hear!

  3. While it is true that liquids expand as temperature rises, virtually all fuel storage tanks at retail pumps are below ground and insulated from daily heating. Try touching the metal part of the nozzle while you are pumping… it will be cool to the touch.

  4. The nozzle is cold because the gas evaporates by absorbing away the heat. Something like rubbing alcohol on your skin – it will be cool while the alcohol evaporates.

  5. Jay Rogers says:

    Kurt is right. The gasoline is the same cool temperature all day long because it is coming from an underground tank. Selvan is wrong. There is no evaporation of the gasoline taking place as it flows through the nozzle.

  6. Mark Cloud says:

    Glad to see that there are at least a couple readers got it right. The fuel will not change temperature from day to night … not even half a degree. Consider how much energy it would require. Additionally, there is very little time for the fuel to heat up in transit in the pump. If the fuel only expands by 1.7% in 30 degrees, then even if the gasoline did heat up by a couple of degrees before it passes thru the metering section, it would only expand by a 0.11%. Wow, that might save me a nickle on a 40 dollar fillup.
    If you want to increase your fuel economy, then try driving 55, tuning up your engine, using iridium plugs, lighten the load in you vehicle, or making sure your tire pressure is correct.

    • According to research, the ground cools overnight. This cooling is not petty, but quite drastic. This eventually cools the fuel in the underground tank, making it the most densest in the morning.

  7. Anonymous says:

    tks abuot his genorositey by morning finance
    reed and rate by alim.com


  1. […] Fill up first thing in the morning. Now the basis for this is a lot more scientific that I can get into, but it has to do with the air […]

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