buying gas - best time of day?

[bigbrother8]

i read this in a thread at another forum that i hang out at, is it a true statement?

Buy gasoline during coolest time of day - early morning or late evening is best. During these times gasoline is densest. Keep in mind - gas pumps measure volumes of gasoline, not densities of fuel concentration. You are charged according to "volume of measurement".

 

[XS650]

That old story is 98% baloney.

Most gasoline is stored underground where the temperature varies little. It's only above ground for quick trip through the pump and dispenser. Not much time for a temperature change.

If you are concerned about gasoline density, the time to buy it is a couple of days after the tanker has put it in the underground tanks so it has had a chance to cool off from being undederground. Still a miniscule difference.

 

[Colt45ws]

I doubt it. We are talking about a large volume of liquid, usually located in underground tanks, which pretty much stays the same temperature, or at least averages the temperature. Even if the tank were aboveground I doubt the difference would be anything measurable.

----, beaten.

 

[Master ACiD]

there is so much volume in the tanks that the temparture will not change very much at all between 5pm and 5am.

 

[cmhj]

Biggest line of ---- yet.

 

[Dad2leia]

The gas pumps are less busy midday as well, so you don't waste the gas that you'd be putting in in the morning or the evening by having to sit there and wait...idling.

 

[Dominic]

I just buy it when its cheapest... whenever that happens

 

[Vilan]

Gas is made up of lots of different things. I picked one of the major ones, toluene, and looked up the density here.

At 20*C, 0.8669 kg/L. At 25*C, 0.8623 kg/L.

That's a difference of about 0.5%. If you buy 10 gallons gas, it's a difference of about one cup, assuming all the ingredients behave the same. Significant? You decide.

But I'd tend to agree that the underground storage tanks stay at a pretty constant temperature. Maybe don't fill up on a sweltering summer day just after the tanker dropped off a load?

 

[XS650]

Quote:

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I just buy it when its cheapest... whenever that happens

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[Shannow]

Underground tanks are pretty constant temperatures once they have stabilised.

One of the biggest rorts down here was that the trucks are filled at a relatively constant temperautre, then they spend the trip up the mountains in the full sun, picking up temperature.

Invoice is the volume dropped, not the volume loaded. Volume dropped then reduces as it sits in the tank.

Down here Tuesday was the cheapest day to buy petrol, with Friday/Saturday the worst. All due to "market forces"

An enquiry was launched into petrol pricing, and suddenly there was no best day.

 

[SKUNKY]

This is one reason that I fill up at 1/2 a tank..the temp in fuel tank will mix with the cold fuel giving me a more uniform temp..that way my engine won't catch pneumonia..I'm ANAL..

 

[Eddie]

I heard that gas station pumps in Canada are "temperature compensating"

 

[Durango]

Quote:

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That old story is 98% baloney.

Most gasoline is stored underground where the temperature varies little. It's only above ground for quick trip through the pump and dispenser. Not much time for a temperature change.

If you are concerned about gasoline density, the time to buy it is a couple of days after the tanker has put it in the underground tanks so it has had a chance to cool off from being undederground. Still a miniscule difference.

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This issue was on the news a couple months ago. Gas is cold under ground but the quantity might changes at the nozzle. Their's no real answer to quality control the temperature from the under ground tank to the nozzle in the industry.

Still better to fill in the early morning or night time.


Durango

 

[XS650]

Quote:

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I heard that gas station pumps in Canada are "temperature compensating"

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I think you are confusing that for the heaters that are in the GWN gas storage tanks to keep the gasoline from freezing solid.

 

[mechtech2]

Like mentioned, a fuel tanker truck will have it's contents much warmer than deep underground tanks. [mild weather].
Right after filling the storage tanks would be the worst time, then.

 

[ARB1977]

I guess the only way to test that theory is take a gallon of gas in the middle of the day and compare it to a gallon of gas in the morning or at night.

 

[Vilan]

Quote:

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I heard that gas station pumps in Canada are "temperature compensating"

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Yeah, I was just thinking that most (all?) pumps I see up here will say "volume dispensed is adjusted to 20*C" or something like that. I guess they have a thermometer in the storage tank and adjust based on that. So in that case it wouldn't matter when you fill up.

 

[Durango]

I suppose wether it's finely controled or not the worst time of the day your fillup might result in a slightly less gas in your tank. Wether it ammounts to perhaps less than a dixie cup maybe it doesn't matter after all.

For myself since California gas is hitting the roof again I want all of what my money is buying. Back to Costco for me.

Durango

 

[cowpie1]

OK... from one who has tanked fuel.

Most of the fuel coming out of the terminals is warm in relation to ambient temps. ALL storage tanks today below ground are double hulled or better due to EPA standards. I realize that things are cooler underground, but the fuel will stay relatively warm for quite some time. Above ground, the fuel will stay warm and not cool off that much overnight. Only if the fuel is sitting for quite some time in these tanks (such as a low volume station), is there any cooling that makes a difference.

Now the fun part... The fuel is temperature compensated (60F) at the terminal for sale to the retailer, but the fuel is not (except in Canada) temperature compensated at the pump. A lot of us are paying for warm fuel and not getting the BTU quantity we are paying for. For a 20 gallon fillup, the fuel temp of 80F is causing expansion of about 1 quart or more. You are paying for 20 gallon but getting less than 20. Not a whole lot, but multiply that over all the fuel pumped in a year and it comes out to several billion dollars spent for fuel not gotten. That is why there is current activity in the U.S. House to mandate temperature compensated pumps by 2010.

Just .02 cents worth.