Airline Pilot Question:

The winglet will allow a new airplane that already flies farther, higher and more economically than competing products to extend its range, carry more payload, save on fuel and benefit the environment. Unlike traditional winglets typically fitted at abrupt angles to the wing, this new advanced "blended" design gently curves out and up from the wing tip, reducing aerodynamic drag and boosting performance. A Next-Generation 737-800 equipped with the new winglet will be able to fly farther, burn 3 percent to 5 percent less fuel, or carry up to 6,000 pounds more payload. Quick answer is...it reduces drag cause by aerodynamic forces acting on the wingtip. Because of that it gets less fuel burn or greater cargo loads, or both.