As most automotive investors know, Ford Motor Company 's ( F ) profit largely revolves around its F-Series pickups, which sell in the most profitable segment in the U.S. market. Full-size pickups, in this case the F-Series and General Motors ' ( GM 0.52% ) Chevy Silverado, are also the two best-selling vehicles in the U.S. most years by a wide margin. That means full-size pickups offer the fastest way for Detroit automakers to gain or lose market share, as well as massive profits.