MPG While Towing

[MasterDiver]

We towed a new trailer back to OH from FL. I have a 13 LTZ Hoe with HD Tow pkg. We bought a ~5700lb camper (loaded with stuff) and towed it back from FL to OH on I75. In flat FL we got 10 mpg, once we hit hills in GA dropped to 8 mpg then through mountains in TN and KY dropped to 7 mpg. Also a lot of hunting between 4th and 5th. Except for when in actual mountains I left the Tow Trailer setting off. So we would drop to OD when going downhill. I monitored the tranny temp and it never really got above 190 and ran cooler as the temperate outside dropped, except in stop and go traffic before and through Atlanta. The engine temp never moved. We kept speed right around 65. Above that seemed to cause it to run in 4th more. So my questions are:
Where is the sweet spot between speed and mileage? I would like to do better if possible?
Should I leave the Tow Trailer setting on when pulling or is it OK to to get into OD?
How much of that hunting between gears is acceptable?
Any other input?
Thanks.

 

[rkeats]

MPG

Hi,
I use my 2008 Tahoe LTZ to tow my 26 foot boat from Cincinnati to Lake Cumberland, so all rolling hills. The boat and trailer weight in at about 6500 or more and I average about 10 MPG. However, a boat is more streamlined then a big box camper and does make a difference in MPG. "Normal" mileage not towing averages about 14.5
Hope that helps.