Gasoline and diesel fuel expand when temperatures rise and shrink when it cools down. That means in warm weather you're probably getting less than you pay for. The difference may not be much for a single tank, but it all adds up. "The overcharge is rampant, legal and hard for consumers to spot. But it's no secret," says the Los Angeles Times, which reports that "oil companies acknowledge and regulators allow" the retail sale of fuels that have expanded because of warm temperatures, but don't deliver the amount of energy they're supposed to. Elizabeth Douglass wrote the story.