Costco has been selling gasoline since 1995. For more than three decades, its fuel stations have operated as one of the most powerful membership incentives in all of American retail — a concrete, daily-life demonstration of the value that a Costco membership card unlocks for its holders. On any given day at virtually any Costco warehouse in the country, the line of vehicles waiting to access member-only fuel pricing stretches long and moves steadily, a visible testament to th