2014 Sunseeker 2650S (Ford V-10) towing 5,000lb car/trailer combo:
Before Scan Gauge E - 8 MPG with cruise control averaging 60-65 MPH.
After Scan Gauge E - 9 MPG kicking cruise control off when going up/down hills at 55 MPH.
The Scan Gauge E really shows you when/how you loose your MPG. In hilly NYS and PA driving, I've seen 3 MPG (instantaneous) with the cruise control trying to keep speed up a hill. Kick the cruise off and let it slowly decrease speed and it doesn't drop below 5-6 MPG in most places. Going down a long hill the cruise control will downshift and you'll loose free gravity-based energy. Kick the cruise off as you approach the downshift point (about 4 MPH above what it is set at) and you may speed up to 70 MPH (air resistance limited in most places) and you'll see 999 MPG for the length of the down-hill run.