June 09, 2007
Silly season at the gas pump
Like most things, gasoline is bigger when warmer. Since the gas pump measures volume as you fill your car, you get less gasoline by weight, therefore less energy, when the gas is warm than when it's cold. So far so good, but here the failure of high school science and economics education starts to send the story into never-never land, because grownups in congress and California are spending time, and writers for grownup newspapers are using ink, trees, and your attention, for some truly vacuous political theater.
Before this Emily Litella moment goes any further:
(1) The pump is a pump, not a tank. The tank is several feet underground, so the gas you pump into your car through the pump is neither hot on a hot day nor cold on a cold day. The first gallon probably warms up a little going through the a pump that's been standing around in the sun, but where air temperatures vary over the year by 30C (54F), soil temperatures about four feet down, where the tank is, change about 15C. The volume change in gasoline over this range is less than 1.5%: in the depth of winter, you get 3/4% more for your money, and in the dog days, 3/4% less. (After the gas is in your tank, it expands or shrinks, but you don't lose anything from this.)
[Distributors and refiners use temperature-compensated meters because their product is mostly stored above ground, in the sun, with a much wider temperature range, and because the cost of the compensating meter is spread over thousands of times as many dollars' worth of gas.]
(2) This is about 40c each way on a typical fillup. People who resharpen razor blades have dozens of pennies to save by only buying gas at night, at stations under a nice dense tree cover.
(3) The proposal in the air is to add temperature compensation to every gas pump in America. Retailers will have to pay for these gadgets somehow ($2000 +/- per pump), and during the summer they will get maybe a penny less for each dollar's worth they sell. Do we imagine prices will just stay the same, or that the next time prices change in the summer they will end up at three more cents per gallon than they would have without the compensation (and go down 3c in the winter)? To think prices won't change to account for the correction, leaving you exactly where you are now miles-per-dollar-wise, you have to believe gas prices aren't competitive (and there are lots of people anxious to sell you a gouging conspiracy already), and that government can somehow keep track of that extra three cents amid all the other ups and downs of retail prices and suppress it (and of course, require that it be tacked back on in the winter).
Doesn't Dennis Kucinich have something more consequential to worry about? Assemblyman Davis? Cong. Cummings?
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