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Date:         Fri, 30 Nov 2012 15:56:57 -0600
Reply-To:     mcneely4@COX.NET
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Dave Mcneely <mcneely4@COX.NET>
Subject:      Re: Gas consumption higher in winter?
Comments: To: OlRivrRat <OlRivrRat@comcast.net>
In-Reply-To:  <99DA2669-6C13-4281-AFEE-6AFBDDD4A68C@comcast.net>
Content-Type: text/plain; charset=utf-8

---- OlRivrRat <OlRivrRat@comcast.net> wrote: > This from Wikipedia

Which is in complete agreement with what I said, as is the other site you referenced. But, I did not know that a standard commercial gallon was measured at 60 F. To compensate, the pump would have to measure the temperature, and integrate an algorithm to adjust the metered volume to what that volume would be if the temperature were 60 F. Since chips and programming are now cheap, that would not be hard to do, but it would add a tiny increment to cost.

thanks for the links. mcneely > > "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 @ 60º 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 @ 80º is 233.7CuIn > >> > >> & @ 30º 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 >

-- David McNeely


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