Aviation Partners Inc. - Seattle WA - Blended Winglets for Boeing 737, 757, and 767
We all know that the main reason for winglets is fuel saving.
But they do increase the range, even if only by a small amount.
Increased range for a given fuel is a saving.
If you won't believe me or B&B then believe the people who make them for Boeing.
Right hand side about half way down "Increased payload-range"
For a given payload the aircraft will fly further with winglets than without.