How Big can a 5.2 get?

Our gas prices have been dropping this winter which is highly unusual. With an exchange rate of 1.33; the price equivalents of 87E10 are from as high as 6.49 per USg last fall, to currently 4.79 per USg.
Just to compare; a 2 liter bottle of Coke costs the equivalent of 8.96/USg.
And jug of milk is 9.68/USg equivalent, of which I buy 3 per week,minimum, of which I drink 2 by myself. I love milk!