Temperature dependence of gasoline volume


#1

My husband usually fills our gas tank, while I sit in the car and fill in “the book” ( yes, he’s just like Topher). During all that sitting and waiting, I have noticed that gasoline pumps all say that the gasoline volume is corrected to 15 C (or 60 F in the States). Thus even if there might be a slight difference in volume due to the outside temperature, the pump will automatically correct for it. I think that listener owes his girlfriend a mojito.


#2

Here in “the States,” automatic temperature conversion at the pump is not the standard. I think you owe someone a mojito.


#3

The US pumps don’t correct for temperature, they deliver on gallon, regardless of temperature. Underground storage tanks vary only seasonally with temperature, so cold winter tanks will deliver more pounds of gas per gallon, warm summer tanks less.


#4

The US does not, as has already been stated, correct for temperature. It can make more of a difference than one might imagine. I filled up my 1971 Toyota Landcruiser early one May morning and the daytime temperature climbed to nearly 90°F. Gasoline was flowing freely out of my filler cap after the car had been sitting for several hours. I estimated about 1.5 quarts flowed out due to expansion. My Toyota had a fuel tank that was under the passenger seat and was painted black. Since the top was off the vehicle the sun shone directly on the side of the tank. Most fuel tanks would probably not heat the fuel as much since they are no in direct sunlight.


#5

It seems to me that the gasoline tanks are all or mostly all beneath the frost line. The tanks are also quite large and will have a huge thermal mass. I doubt that the temperature of the gasoline changes an in the ground. It might change some while flowing through the above ground pump system, but probably not much since it flows quickly.


#6

See http://www.consumerwatchdog.org/resources/DPReportHotFuelUSAJune07.pdf titled “American Consumers will pay a Hot Fuel Premium of 1.5 Billion Dollars on Regular Gasoline Purchased during the Summer 2007”. 30 degrees F causes about a 2% change in volume.


#7

Interesting that analysis doesn’t talk about the ‘cold fuel benefit’ we get in the winter. A bad piece of work


#8
Interesting that analysis doesn't talk about the 'cold fuel benefit' we get in the winter.
Of course not; consumers aren't concerned with getting more than they pay for. But, don't people generally drive more in the summer than in the winter? Causing more gallons of fuel to be sold when temperatures are above 60 degrees? And aren't fuel prices usually higher in the summer also? So a 2 percent expansion on higher-priced summer fuel is costing more money than the savings of a 2 percent contraction on the lower priced fuel during the winter.

I’m sure it was mostly left out because no driver is concerned that he’s getting more fuel than he’s paying for, but I also wouldn’t be surprised if the cost of fuel that is being overpaid for is far higher than the savings to consumers on fuel that’s under 60 degrees. Fuel stations in Canada adjust at the pump - it saves the station owner money overall. I’ll bet fuel stations in the southern U.S. wouldn’t be in favor of adjusting at the pump though!


#9

It also seems folly to mean to add things such as nitrogen to the fuel. Ther eis no oxidation energy in nitrogen. It only takes up space. You end up paying for an iinert gas thatcame from the air and returns to the air Nitrogen to clean valves…poppy cock.


#10
It also seems folly to mean[sic] to add things such as nitrogen to the fuel. Ther eis[sic] no oxidation energy in nitrogen.
So don't buy Top Tier gasoline then. But all gasoline has a minimum amount of required detergents and deposit control agents, so whether you buy fuel with nitrogen in it or not, you're paying for stuff that's "taking up space," without adding any energy or oxygenation to the fuel.

#11

I’d be amazed that there would be much of a difference. Gas is stored in underground storage tanks. Should be a constant temp of about 56 degrees. I wonder how much the gas can cool from the time it’s pumped out of the ground into ones gas-tank.


#12

My last sentence should say…

I wonder how much the gas can warm from the time it’s pumped out of the ground into ones gas-tank.


#13

Not all that much unless it’s passing through heated lines. Think of how warm (or more properly, cold) water is after passing through a garden hose on a hot day. Once you flush out the water that was sitting in the line and heating up, the water’s cold even after going 100’ down a dark hose in the sunlight.


#14

There is alot of difference when it comes to the "oxygenated fuels introduced in th eWinter months here in NH. When that switch occured, my 2001 Eclipse V6 would drop in mileage from 30 to about 24…very abruptly. The oxygenared fuel pollutes less per gallon but it also has much less energy per gallon so I burn more of it to go the distance I used to. My mileage would return to higher levels at about mid-April. Once again, an energy company that is selling energy by the gallon (doesn’t make sense) has much incentive to “volumize” that gallon with the cheapest volumizer available…nitrogen is everywhere and is inert for our process… I think the practice of fuel blend changing is of questionable value. I’d l;ike to see the science and experimental results with pollution being measured in some other dimension than **** / gallon.


#15
There is alot of difference when it comes to the "oxygenated fuels introduced in th eWinter months here in NH.
Butane is added in winter months to increase volatility. Butane has a very high vapor pressure, and adding it in the winter makes your car start better and causes your catalytic converter to start up quicker, reducing emissions.
selling energy by the gallon (doesn't make sense)
What better way is there to do it? And fuel prices do tend to reflect the energy content of that particular fuel. E85 has a much lower energy content due to all the ethanol, and it's price reflects that. Winter gasoline has fewer BTU's per gallon due to components added to it to increase Reid Vapor Pressure, and winter gasoline is cheaper than summer gasoline.

Maybe you could invent a pump that tests the energy content of a fuel as it’s being dispensed and charges accordingly. And then when we’re paying based on energy content, we can start paying for food based on its caloric content. I bet that would reduce the number of low-income, obese people in this country!


#16

Now you’re well skilled in rebuke and loosely correct chemical knowledge. You toss them around like a very skilled politician. I’m of a background and education level that I do understand those carbon to carbon double bonds and how they become more volatile–aromatic as the decrease in length and mass. So, instead of attacking what you find easy to, add something rather than conflicting. Weight would be a fairer tool of measure for gasoline… You will notice naval, railroads, aviation, etc spaek of fuel weight, not volume. seems as though heat does change volume significantly and my goodness, you can figure the available energy more readily with mass rather than coming up with a temperature-dependant, ad-hoc conversion. No, not practical for cars and the like but I just wanted the curious to kniow where I’m coming from. Meth, eth, but, prop, pent…etc to oct for the approxiamte area of gasoline. Now, one of the C=C’S is broken for us already in that butane so it is delivered in a lower potential energy state. With all that aside, we still end up ussing very little of the energy purchased to actual;ly move us. We engineer systems to dissipate that valuable heat…That’s the main point I’m after.


#17
You will notice naval, railroads, aviation, etc spek of fuel weight, not volume. seems as though heat does change volume significantly and my goodnes, you can figure the available energy more readily with mass
Measuring by mass isn't going to do a bit to help differentiate between fuels of different BTU contents, which seemed to be the problem you implied with measuring by volume. 20 lbs of winter gasoline is still going to have less energy than 20 lbs of summer gasoline. And I can tell you from a background in aviation that light aircraft do measure fuel in gallons - just like a car. In large aircraft, fuel is measured by weight. Not because it somehow gives a better approximation of energy content, but because maximum takeoff weight and center of gravity balance are crucial - a passenger plane fully loaded with passengers and baggage can easily be overweight with a full load of fuel. I don't know about ships and trains measuring the weight of fuel; I'll have to take your word for that.

#18

The reason the specific fuel consumption of aircraft engines is rated in hp-hrs/lb instead of hp-hrs/gal is because the BTU content of a gallon of gasoline varies a lot more than the BTU content of a pound of gas does.

Butane 21,896 BTU/lb
Pentane 21,706 BTU/lb
Hexane 21,416 BTU/lb
Heptane 21,326 BTU/lb

It looks to me like adding butane actually increases the BTU/lb even though it lowers the BTU/gallon.


#19
The reason the specific fuel consumption of aircraft engines is rated in hp-hrs/lb instead of hp-hrs/gal is because the BTU content of a gallon of gasoline varies a lot more than the BTU content of a pound of gas does.
I've never seen an aircraft engine rated in hp-hrs/lb - but you can't rate an engine for fuel consumption anyway because it's entirely dependent on the aircraft it's attached to, it's the aircraft in its entirety that would be rated for fuel consumption. Additionally, gasoline-powered aircraft measure fuel burn in the cockpit in gallons per hour, not pounds, so any fuel burn rating in the POH is going to be gallons per hour. It's jet aircraft that measure in pounds per hour, and they don't burn gasoline. I should have mentioned earlier that, even though a jet measures fuel in pounds in the cockpit and on it's computer controlled filling port (if it's large enough to have one), it is still measured in gallons for the purpose of calculating the sale, just like when you fill up your car.

#20

You again pick on a point that had nothing to do woth the original intent of what I said. However, mass does equalize the advantages of volumetric change due to heat.—nuff said on that. If you can guaratee the consistency of the chemical composition, then you’re set. I’ve bought propane before that was not trustworthy for that and would only heat the grill I had to a little over 250 deg…I got ripped off. Weight is typically an easier thing to measure than volume beacuse of its static nature…you have to measure volume indirectly via flow and no matter how you look at it, it is more difficult and less accurate…that aside again, I want to make sure you don’t have anything to say about the questins I had about efficiency. Fire att will.