Talking about fuel saving is a very difficult issue.
The BBJ type winglets are of a different type from what we see on fast longhoulers. But they are more efficient - when they work best.
But they are not well suited for high Mach numbers. And they are very much "one alpha" winglets, meaning that they only work well within a narrow window of wing angle of attack (= alpha).
They are most likely optimised for a 737 avarage cruising speed (around M=.76) at 30,000 ft. with an avarage weight.
If ATC forces a heavily loaded plane high up in thin air, then alpha may increase to a level where the winglets do more damage than good. In the opposite scenario, on a light plane kept low they might work best at a low speed like M=.65, but if schedules demand that you keep M=.75, then the winglets may just give you extra drag costing extra fuel.
So the gain in fuel efficiency will depend very much upon how freely you will be allowed (by ATC) to fly the plane at its optimal performance.
Only one thing is sure: If Boeing claims for instance a 3% gain, then your gain will be less than 3% in everyday work. How much less, it depends...
Always keep your number of landings equal to your number of take-offs