Average with a 8500# (64 sqft frontal) bumper-pull over 13K miles has been about 10.9 mpg.
EDIT: I rarely tow over 65 mph (just to pass).
2014 ORV Timber Ridge 240RKS,8500#,1250# tongue,44K miles
690W Rooftop + 340W Portable Solar,4 GC2s,215Ah@24V
2016 Ram 2500 4x4 RgCab CTD,2507# payload,10.8 mpgUS tow