Jun
19
2007

Gas pains: Higher temperatures lower your fill-up

Pumping less: When the temperatures go up, the volume of fuel you gas you pump into your car goes down according to the "hot fuel" effect of physics. It could cost you between three and nine cents a gallon on hots this summer. (Photo by architeckt2)
Pumping less: When the temperatures go up, the volume of fuel you gas you pump into your car goes down according to the "hot fuel" effect of physics. It could cost you between three and nine cents a gallon on hots this summer. (Photo by architeckt2)
Just when we thought we were paying too much for gasoline these days, here comes some even worse news.

Depending on the air temperature at the time you fill up your tank, you might be getting less gas than what the pump is telling you. That difference could be costing us between 3 to 9 cents per gallon, with that loss factor going up as the temperatures go up.

Is this another example of oil companies ripping off consumers? Maybe a little bit. But it’s a lot of science – actually physics -- at play.

I was just reading a story in today’s Star Tribune about this phenomenon called “hot fuel.” Here’s quick summary on how it works.

The set industry standard for a gallon of gasoline is 231 cubic inches of the fluid at a temperature of 60 degrees. But as the temperature goes up, gasoline expands and it takes a larger amount of the fluid to create the same amount of energy.

Gas stations don’t take into account temperature changes at the fuel pumps. They pump the same amount of fuel as one gallon no matter what the temperature may be. And while that may result in a rip-off in summer time, when gasoline expands, consumers get a flip-side benefit in the wintertime, when gasoline pumped below 60 degrees actually contracts and you get more energy for your dollar at the pump.

Interestingly, the state of Hawaii back in the energy crunch of the 1970s recallabrated its gas pumps to reflect the volume of gasoline to be set at 80 degrees, a much more standard and uniform temperature there. At that temperature, a gallon of gas is actually 234 cubic inches.

There are some Congressional leaders asking for an investigation into this gasoline volume discrepancy. Oil companies, predictably, say that the cost of factoring in temperature changes in pumping gas will be too high.

Judging from the weather here in Minnesota, I’m not too hot in getting government involved into this. Judging that are temperature are under 60 more than they’re over that level, I think we’re getting a pretty good deal. But residents in the south and western U.S. are probably getting a bad deal out of the situation.

What, if anything, should be done about this gas situation? Share your thoughts here with other Science Buzzers!

Your Comments, Thoughts, Questions, Ideas

Norita's picture
Norita says:

Here are more relevant facts on hot fuel, www.turndownhotfuel.com

posted on Mon, 06/25/2007 - 2:37pm
Anonymous's picture
Anonymous says:

How much does the fuel temperature vary in underground tanks?

In Iowa, the ground never freezes six feet down. If the underground tank is 3-13 feet down, would the temperature change significantly during the day? I doubt it. Would it change much from the height of summer to the coldest part of winter - yeah, some.

I think this is a non-issue.

posted on Thu, 11/22/2007 - 9:16am
Anonymous's picture
Anonymous says:

With storage tanks underground, the temperature should stay fairly close year round, anytime of the day.

posted on Fri, 06/13/2008 - 4:58pm
Anonymous's picture
Anonymous says:

Yes, but wouldn't the pressure underground take over the storage tanks (temperature wise??).?

posted on Sat, 06/14/2008 - 4:55pm
Anonymous's picture
Anonymous says:

It is the temp or the gasoline that matters NOT the temp of the AIR.

posted on Fri, 06/27/2008 - 12:44pm

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