Boeing Aero 17 -
Gross fuel mileage improvement with winglets was recorded in the range of 4 to 5 percent. Taking into account the weight of the winglet and the related wing structural modifications, the net performance improvement was approximately 4 percent for long-range flights (fig. 6). Low-speed testing showed a significant reduction in takeoff and landing drag and a significant benefit in payload capability for certain operations (fig. 7).
Runway performance improvement, second stage climb improvement, cruise improvement, approach drag improvement.
I believe it also improved climb performance.