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Re: AVP MPG Questions
THe fuel station fuel pump is temperature compensated, so what it indicates are equivalent gallons as if they were measured at a constant temperature. Read carefully on the fuel pump meter: it says so. So technically speaking, it is a mass meter rather than a volume meter....although the reading is given in equivalent volume. Between two fillup, the temperature of the fuel in the station fuel tank is rather dependant of its under ground solid surroundings, not the atmospheric or your tank temperature so there is a good chance two consecutive fill-ups will be made at quite the same fuel temperature...otherwise indeed a tank of cold fuel would contain more fuel mass than the same tank of warm fuel..but it would take a rather large temperature difference to be significant. a 10°F variation corresponds to a mass differeence of 0.4%....meaning about 0.1 mpg equivalent..less than the margin of error of calculation.
Indeed fuel mileage calculation using tank fillup can bear a large margin of error, due to the air gap that is left in the tank; the actual level of the tank when it stops the gun by throwing out will vary depending on terrain slope and uneven car load..and depending on how long you insist to fill-up to the edge with small increments. However makling measurments using the sum of several consecutive tankfuls spreads the uncertainties over the number of fillups, so you end up with something quite precise. That also explains why calculations using one fill-up and then the next each by itself can suggest wide variation in apparent fuel burn.
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Last edited by LMP : 01-11-2007 at 02:00 PM.
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AVP MPG Update
Re: AVP MPG Questions
