i_like_spam writes: Motorists in 13 states have filed lawsuits against big oil companies and gas retailers alleging unfair pricing practices related to fuel-pumping temperatures. From an industry standard developed in the 1920's, the price for a gallon of gasoline is based on the density of the fuel at a temperature of 60 degress F. A gallon of gas at higher temperatures is less dense, and therefore contains less energy. The lawsuits claim additional costs of 3 to 9 cents per gallon without temperature adjustments. The fuel industry claims that the costs of installing temerature-adjustment sensors on every pump would be prohibitively high. These sensors are already installed in Canada, however, where the colder temperatures favor consumers.