What role do the winglets on the next-generation 737 play?
The wing tips calling as "sharklet" at Airbus A/Cs and "winglet" at Boeing A/Cs. It reduces the tip vortex and helps to prevent from airflow seperation at wing tips. It have positive effects on both fuel consumption and turbulance making. Negative effect of the additional part is increase of the drag coefficent but you can keep it negligible againts the positive effects.