Not just inflated prices but inflated fuel

[snopes]

Here's another way you're getting pinched at the pump: Paying for, say, five gallons of fuel doesn't mean you're getting a full five gallons.

Fuel expands when temperatures rise. And because gasoline station nozzles don't adjust for the change, motorists and truckers end up with less of the energy that keeps engines humming.

http://www.latimes.com/business/la-f...,1724695.story

[Not_Done_Living]

Thats silly.. the technology exists... in Ontario every single gas pump says "price adjusted to 15 Degrees Celcius".

Why can't they do that there?

[kitap]

This does explain the "Another tip to save money at the pump: pump at night or before the sun rises" comment one of the local TV news reporters said in a story. They didn't explain and I was mystified.

[TrekkerScout]

Originally Posted by Not_Done_Living

Thats silly.. the technology exists... in Ontario every single gas pump says "price adjusted to 15 Degrees Celcius".

Why can't they do that there?

It's a matter of "can they do it" versus "will they do it." Sure, they can add temperature readjustment equipment to each and every pump. However, it would cost the stations thousands of dollars per pump to install. Will they do it without government regulation? Not likely since it interferes with their bottom line.

Here's the thing. 15C is the standard temperature used for ambient temperature as a basis for measurements. All adjusted for 15C means is that the amount of fuel pumped is correct for the temperature at the time of delivery, so if it's +30 on delivery day, the amount pumped is already adjusted. There's no equipment or device, electronic, or mechanical that changes temperature of the fuel on each pump in Canada. Fuel tanks, generally underground, stay at a constant temperature, and as a result, temperature above ground does not influence the temperature underground much. According to the article, expansion means you are getting less fuel at higher temperatures than cooler. OK, but that expansion and cooling occurs AFTER the fuel is pumped from underground. You still have the amount of fuel you pumped, but it will expand as the day gets warmer again. If the trucker cited in the article had loked at his tank later in the day, the 3 gallons "lost" would be right back. Another thing is diesel fuel in trucks passes through the injection system, and excess fuel not required for operation is recycled through the system, heating and expanding it. So, if he's fuelled with an engine at operating temperature, there is going to be heated fuel already in his tank. As it cools, it will look like less fuel, but in reality is still the same amount, just cooled. To compare, fill a 2 liter bottle with cold water, another with boiling water. Check the water levels when both are at room temperature.
The article also overlooks the fact that winter driving, especially when temperatures are sub-zero, uses MORE fuel than summer driving, so the fuel "lost" to expansion is a red herring at best. For example, I can drive on average 900 kilometers on a tank in my car in summer, but only around 780 in the winter. I still pump in 90 liters of gas when empty, but I go further in the summer, even with the air conditioning on.

[jimmy101_again]

Originally Posted by snopes

Here's another way you're getting pinched at the pump: Paying for, say, five gallons of fuel doesn't mean you're getting a full five gallons.

Fuel expands when temperatures rise. And because gasoline station nozzles don't adjust for the change, motorists and truckers end up with less of the energy that keeps engines humming.

http://www.latimes.com/business/la-f...,1724695.story

Actually, the temperature has nothing to do with whether you get five gallons of fuel. You buy it by the gallon not by the energy content. So the first sentence is not true, though the second sentence is true.

JD65 got it exactly right. The fuel is stored underground, where the temperature changes very little from ~60F, regardless of how hot or cold it is outside. Very little heat is going to be transfered into the gasoline by the plumbing between the storage tank and the gas pump's meter.

A bigger issue would be filling your gas tank up to the brim on a hot day. When you stop filling, the gas is at ~60F. If it is 95F outside then eventually the gas will warm to that temperature, expand, and escape from the tank. (Modern cars in the US are supposed to capture the escaping fuel but ...)

[Wolf333]

JD65, I was thinking the same as you until I read the entire article. They are talking about the temperatures in the underground tanks, which can reach almost 80 degrees in warm climates.

The trucker's story was meant to be anecdotal evidence to back up the actual evidence, but it was poorly placed at the beginning of the article.

[Joostik]

A sampling by federal regulators of fuel temperatures in underground tanks at service stations from 2002 to 2004 found a wide range above and below 60 degrees. The limited survey in California found fuel temperatures averaging 74.8 degrees, with a low monthly average of 64 degrees and a high of 83.

"The information that they got from California really shocked me," said Dennis Johannes, director of the state Division of Measurement Standards. "The average temperatures were a lot higher than what we expected."

Johannes launched statewide fuel temperature tests last month. Readings will be taken through December, but an early report "tells me that already the fuel is over 60 degrees, and we're not even into summer."

But are these daily fluctuations as well as just seasonal? If they are merely seasonal it woudn't make much difference what time of the day you fill up. On the other hand, if they are daily differences would isolation not be a better option than instaling expensive regulators?

Anyway, I'd say its something that should mostly concern professional drivers. I can't imagine any private person getting up in the middle of the night to get some marginally cheaper fuel.

[Singing in the Drizzle]

I just did some research. The thermal expantion volumetric coefficient for gas is .000950 per deg C. If I remember my math rightly. If the gas in the ground is 10 C warmer during the day than the night and I was filling my car with 10 gallons of gas during the day. I would lose (10C X 10gal X .000950) .0095 gallons of gas (about 1/100 of a gallon). Are the flow meters even accarate to +/- .01 of a gallon?

[RichardM]

Depending on the depth of the tank, there is very little daily variation in temperature. I don't remember what depth the temperature becomes constant and I'm too lazy to look it up. But I do know that the temperature will not vary by 10 degrees. And yes flow meters can be that accurate. What accuracy is required of gas pumps, again, I am too lazy to look up but I know it is set by state statute here in Texas.

[Alchemy]

Originally Posted by Singing in the Drizzle

I just did some research. The thermal expantion volumetric coefficient for gas is .000950 per deg C. If I remember my math rightly. If the gas in the ground is 10 C warmer during the day than the night and I was filling my car with 10 gallons of gas during the day. I would lose (10C X 10gal X .000950) .0095 gallons of gas (about 1/100 of a gallon). Are the flow meters even accarate to +/- .01 of a gallon?

It'd be 0.095 gallons of gas. A 10 degC change in temperature would create an error of 1%.

The tightest NIST error tolerance for gasoline dispensers is 3 cubic inches per 5 gallons test draw, or 0.3%. In the US, gasoline is always dispensed by volume, not by mass (there is no temperature-corrected volume). Some stations have automatic adjustments for temperature variation - the temperature affects the size and flexibility of the pipes and other equipment, and the viscosity of the gasoline, which could change volumetric flow rate - but the gasoline is still dispensed in volume, not mass.

It is apparently a given that the density change of gasoline in a particular location is not significant. Gasoline stations operate on thin profit margins, and a significant change in the gallons of gasoline they buy and the gallons of gasoline they sell would make for bad business.

Gasoline sold in large volumes between distributors and to stations is temperature-corrected because if you're buying 6000 gallons of gasoline at a time you really want - and are able to get - a much higher accuracy than if you're buying 10 gallons of gasoline at a time. Additionally, that fuel sitting in a tanker for a day or two is going to suffer much higher temperature variation than the fuel in a UST.

The stupid bit of the story is that the people who are so outraged don't seem to realize the error works both ways, and for every penny the station steals from you when the UST is at 61 degrees, you steal another penny back when the UST is at 59 degrees.

The moron trucker didn't lose 3 gallons of gasoline. It's more dense and will give him higher fuel efficiency, and combined with the cold air he'll get really good mileage. Truck drivers who are good at their jobs understand this and everything else there is to know about their fuel.

Regional UST temperature variation is a potential factor in the differing price of gasoline in warm and cold climates, though it's pretty insignificant compared to differences in taxes. I think heavier blends are used in warmer climates as well to offset this.

Very long NIST fuel station testing PDF:
http://ts.nist.gov/WeightsAndMeasure...Course_302.pdf

Sound and fury, no significance.