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The Organizer
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Discussion Starter #1
As I stated in another thread, there have been multiple warnings about not getting your money's worth at the pump if you fill up in the afternoon. In the afternoon, the pumps don't compensate for the warmer temperature, and you are actually not getting as much gas, but paying the same amount. Gas expands the warmer it gets. If you bought gas in the hot afternoon, by the next morning you will have less in the tank. Depending on how hot the afternoon is versus the morning temperature, and how much gas was purchased, you could be looking at more than a couple gallons difference.
 

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I think this is completely false. While I understand the theory and everything behind it that there is expansion during the warmer days and contraction during colder days, gas pumps are standardized here in Canada for volume at 15 degrees Celsius. So, weather it be -30 C or +30 C, the gas in itself will remain at 15 C.
 

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I've heard this same argument for years without and definitive conclusions. Personally, I've never been able to tell any difference where I buy gas. Doesn't matter what time of day or what the temperature is.
 

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I bet there is some tweaking going on even with that "standardization". I wonder about that as I'm filling up staring at that statistic and if I'm actually getting close to what it says on the screen.

A friend from serbia was telling me stories they'd dilute the gas with water, and if they did it too much your car would stall out shortly after leaving the station. Lots of stories of gas attendants being pummeled for cheating that much, cheating a little is accepted (expected?) so he tells me. His stories a kind of funny because he hasn't quite grasped some of our slang. He says "People would go back and beat the s*** in him" instead of "out of him" hehe.

Forgot to mention, the news we watch every morning just mentioned this too. Guess they use the same newswire hehe!
 

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Never found any difference either, and here in Canada we have cold winters and hot summers, no matter what time of the year I get the same mileage on a tank of gas.
 

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Discussion Starter #6 (Edited)
I think this is completely false. While I understand the theory and everything behind it that there is expansion during the warmer days and contraction during colder days, gas pumps are standardized here in Canada for volume at 15 degrees Celsius. So, weather it be -30 C or +30 C, the gas in itself will remain at 15 C.
Canada is an exception. They have pumps that compensate for the temperature so you always get a gallon (litre) for your money. The story stands in the US. The US gas stations refuse to upgrade their pumps because it would cost $1700 per pump. This also is a bigger factor in warm climates, as the ground is able to vary in temperature more easily.
 

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Canada is an exception. They have pumps that compensate for the temperature so you always get a gallon (litre) for your money. The story stands in the US. The US gas stations refuse to upgrade their pumps because it would cost $1700 per pump. This also is a bigger factor in warm climates, as the ground is able to vary in temperature more easily.
That would make sense. I believe we may have tighter regulations in regards to the sale of gas here in Canada. And even if it was not regulated, in the end with 6 months of summer and 6 months of winter, it would all work out the same.
 

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I understand the principle behind this warning, but not sure how much of a difference the temperature would truly make in volume. Also, isn't earth (dirt) a fairly consistent temp around 60 degrees or so once you go about 4 feet down?

This one would make for a good segment on Mythbusters......
 

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Discussion Starter #11
I understand the principle behind this warning, but not sure how much of a difference the temperature would truly make in volume. Also, isn't earth (dirt) a fairly consistent temp around 60 degrees or so once you go about 4 feet down?

This one would make for a good segment on Mythbusters......
The warmer the climate the warmer and further down the ground is. Add to that the piping that is closer to the surface, and the fact that the gas is entering a very warm gas tank, and it adds up. I was skeptical until hearing it from multiple sources. We have our water supply a minimum of 4' below grade in Albuquerque, and the water temp can vary from 60F in the winter to 80F in the summer.
 

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This has been declared a myth. The difference between filling up in the AM or PM may amount to a teaspoon or so of gas. It simply makes virtually no difference when you fill up.

Same as the myth that filling on a slower pump setting saves gas due to less evaporation. Not in quantities that anyone will ever notice.
 

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true that rodentman sounds a little nuts to me too especially noticing a couple gallon difference thats just nuts. ok so maybe the gas might expand in the underground tanks but the size of the piping or tubes or nozzle don't ever change your still only pushing the same amount through those pipes/hoses, regardless of the expansion. You can't push a quarter through a dime sized hole. If it expands once it gets into your tank which could hold true its not going to be that much especially not a couple gallons. Not to mention the temp of the hose and piping is probably hotter than your gas tank your car is moving and cooling off as your driving the pumps are not. The only theory that does hold some trueness is try not to or don't fill your tank while the tanker, gas truck, is filling cause as it is filling it is stirring up the sedement in the underground tanks and might make its way into your tank. also as far as the couple gallon difference, have you ever worked at a gas station, say for example if you overflow or spill some gas on the ground do you know how much that disperses couple gallons is pretty huge it produces a huge puddle. just my thoughts though prop no argument hear no need for a rebuttal
 

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on a side note what about the theory someone else told me which i don't believe that it is better to fill your tank cause if you have less gas in your tank it will evaporate and that you'll get better milage because its not evaporating? I never fill up my tank, well cause i can't and i try to do it intentially to keep the weight down to try to increase my mileage, or am i getting worse cause it does actually evaporate cause there is less gas in there?
 

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Fuel systems in cars used to be vented to the air. Now they are sealed systems. Any evaporation gets recaptured. It's all quite minor anyway.

I fill my tank when it gets near empty and I get consistent mileage. I have no intention of pushing the car out of the garage, pussyfooting the gas, holding up traffic, or any other penny-ante machinations to get minor savings, if any.

I drive at the speed limits as dictated by the flow of traffic. I consistently get 28-32 mpg which is about what I expected from the Caliber, and I am happy with that.

I consolidate shopping trips and don't just drive around for no reason.

Some of these pussyfooters are so obsessive I think they'd drink their own piss to save on their water bill.

Just get in the car gas it up and go.
 

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Discussion Starter #17 (Edited)
The facts:

  • gasoline expands the warmer it gets
  • the warmer it gets the more it boils off as vapor and the liquid has more space between the molecules
  • water expands too, why do you thing the expansion tank on the cooling system is fuller when hot?
  • if the metering system can't tell the difference between cold fuel and hot fuel, how can it be accurate?
  • during fillup, the warmer the environment, the more gas boils off during that time.
  • fill a sealed plastic gas can in the hot afternoon, seal it and see how collapsed the container is the next morning.
These are simple physics. I'm not saying it's going to amount to a lot, probably on our cars around a cup, but on a big SUV with a 40 gallon tank it would probably be around a couple gallons. If someone can point me to where this has been debunked as a myth with facts to back it up, I'll right this info off. All I've seen is the facts to support it...which I didn't believe at first until hearing it from multiple news sources.
 

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GAS EVAPORATION MYTHS
»Myth: Warmer gasoline expands, while cooler gasoline is denser. Since gasoline is priced by the gallon, buying gas when ground temperatures are cooler means more BTUs per gallon.

Fact: According to Consumer Reports, the temperature of gasoline, as it is being pumped from underground tanks into your vehicle, changes very little, if any, during the course of the day. Any more gas you may obtain is negligible.
Myth or Fact? More gasoline is lost through evaporation when refueling in a 90° F state, compared to a state with temperatures in the 70° F range.

Fact: According to David Champion, Senior Director of Auto Testing for Consumer Reports, gas evaporation during refueling is least during the coolest times of the day. However, with modern fuel pumps, any loss is negligible. In the summer, a decrease in fuel-efficiency may be attributed to another source. According to the EPA in certain high-ozone areas, the EPA mandates the use of special reformulated gasoline (RFG) during the summer months. RFG causes a small decrease (1-3%) in a vehicle’s fuel economy compared to conventional gasoline. However, it is also less conducive to evaporation than regular gas.
Myth: Fill your tank when it is half full in order to minimize gas evaporation and loss.

Fact: According to API, technical changes to vehicle fuel systems have virtually eliminated fuel evaporation loss.
Myth or Fact? Park in the shade; heat from the sun will result in fuel evaporation and loss.

Fact: According to API, technical changes to vehicle fuel systems have virtually eliminated fuel evaporation loss. David Champion, Senior Director of Auto Testing for Consumer Reports, told the Alliance to Save Energy that a small amount of gas does evaporate from older vehicles (1974 or older). According to the EPA, avoid poorly fitted or missing gas caps to decrease evaporation loss.»
 

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Discussion Starter #19
GAS EVAPORATION MYTHS
»Myth: Warmer gasoline expands, while cooler gasoline is denser. Since gasoline is priced by the gallon, buying gas when ground temperatures are cooler means more BTUs per gallon.

Fact: According to Consumer Reports, the temperature of gasoline, as it is being pumped from underground tanks into your vehicle, changes very little, if any, during the course of the day. Any more gas you may obtain is negligible.
Myth or Fact? More gasoline is lost through evaporation when refueling in a 90° F state, compared to a state with temperatures in the 70° F range.

Fact: According to David Champion, Senior Director of Auto Testing for Consumer Reports, gas evaporation during refueling is least during the coolest times of the day. However, with modern fuel pumps, any loss is negligible. In the summer, a decrease in fuel-efficiency may be attributed to another source. According to the EPA in certain high-ozone areas, the EPA mandates the use of special reformulated gasoline (RFG) during the summer months. RFG causes a small decrease (1-3%) in a vehicle’s fuel economy compared to conventional gasoline. However, it is also less conducive to evaporation than regular gas.
Myth: Fill your tank when it is half full in order to minimize gas evaporation and loss.

Fact: According to API, technical changes to vehicle fuel systems have virtually eliminated fuel evaporation loss.
Myth or Fact? Park in the shade; heat from the sun will result in fuel evaporation and loss.

Fact: According to API, technical changes to vehicle fuel systems have virtually eliminated fuel evaporation loss. David Champion, Senior Director of Auto Testing for Consumer Reports, told the Alliance to Save Energy that a small amount of gas does evaporate from older vehicles (1974 or older). According to the EPA, avoid poorly fitted or missing gas caps to decrease evaporation loss.»
Well, now we have conflicting facts. The only undisputed fact is about evaporation from your fuel tank. That hasn't been an issue for years since the advent of carbon canisters. Evaporation only occurs during refueling. I'm still going to refuel in the morning...there are less people at my station refueling then.;)
 
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