This from Wikipedia

"The US liquid gallon

The US gallon, which is equal to 3.785411784 litres is legally defined  
as 231 cubic inches.[1] [2] There are four quarts in a gallon, two  
pints in a quart and sixteen fluid ounces in a pint. In order to  
overcome the effects of expansion and contraction with temperature  
when using a gallon to specify a quantity of material for purposes of  
trade, it is common to define the temperature at which the material  
will occupy the specified volume. For example, for purposes of trade,  
the volume of petroleum products[3] and alcoholic beverages[4] are  
both referenced to 60 �F (16 �C)."

        So lets say that the gas you pump is @ 60� in the  
UndergroundStorageTank, after a short period of time in your GasTank  
it will adjust to AmbientTemp' so in the Summer it will Expand to More  
Gal's & in the Winter it will Shrink to Less Gal's.
        I started looking into this thanks to Costco (where, until recently,  
I never bought gas) as there is a Sticker on their pumps that states  
that the Gal' of Gas that they charge you for is 231CuIn as measured  
by the pump.
        This is an interesting PDF ~ www.nh.gov/agric/news/documents/weights-fuel-temperature.pdf 
  ~ I stumbled on to it earlier when I Googled "gas pump gallon volume"

                                                        ORR ~ DeanB

On 30 Nov , 2012, at 12:28 PM, Dave Mcneely wrote:

> ---- OlRivrRat <OlRivrRat@COMCAST.NET> wrote:
>>         Also keep in mind that the vol' of a
>> Gal'OfGasoline @ 80� is 233.7CuIn
>>
>> & @ 30� it is 227.0CuIn so you actually have less GasByVolume in your
>> tank in the Winter
>>
>> than in the Summer but I haven't really thought through what effect
>> that might have on
>
> Hmmmm........... .  Do you mean that a gallon is not always a  
> gallon?  Is the gallon you cite a gallon at standard temperature and  
> pressure (O C,  760 mm Hg) but a bit bigger at warmer temperatures?   
> Because a gallon is a measure of volume.  The fuel may expand and  
> shrink, but then it won't be a gallon any more, it'll be something  
> else.
>
> Now, if you cited a variable volume for a given mass of fuel (again,  
> the weight but not the mass could vary depending on where the  
> measurement was made), then we'd be getting somewhere.  If you want  
> the same exact amount of fuel regardless of conditions, you need to  
> deal with mass, so as to have the exact same number of molecules.
>
> If you put in a gallon of fuel at one temperature, then the stuff  
> expands as it warms up, there is still no more fuel in the tank, it  
> just takes up more volume, more than a gallon.  Same if it shrinks,  
> it now takes up less volume, less than a gallon.  The amount of fuel  
> does not vary, just the space it occupies.
>
> If you buy a gallon of fuel that is cold, and another time buy a  
> gallon of fuel that is warm, the second time you get less fuel.
>
> All this would suggest that one might get better mileage (miles per  
> gallon) in winter, since by burning a gallon of fuel, one burns more  
> fuel, but other variables seem to obviate that.  At least they do  
> for me, as I get poorer mileage in winter, by subjective judgement,  
> anyway.  Of course, to be sure, we'd need a controlled experiment  
> that is probably beyond our ability to design and carry out given  
> the limitations of available vehicles and ability to control  
> variables.
>
> mcneely