1400 miles round trip, all interstate highway and using cruise control at either 70 or 75 the Hemi gave me 18.5 going down(loaded Jeep) and 21.3 for a round trip total. When I had my 09 Hemi I averaged 18.7 on the same trip and using cruise also. Happy camper here.
15 GC Overland
15 Rubicon Unlimited