Interesting numbers. I drove my 2019 Ram Limited on a round trip of about 900 miles when it had a little over 1000 miles on the odometer. 90% of the trip was interstate and I drove it at about 65 mph. My average was in line with yours. My truck's performance is better than what I expected. I came from a 2011 Avalanche that weighed in at 5259 # with a 5.3L engine. My Ram with options weighs about 6321 pounds and has the 5.7L non-etorque engine. I drove the same trip with my Avalanche many times and usually averaged around the same 20-21 mpg. So, my truck weighs about a 1000 # more, is probably less aerodynamic, but I still am getting decent mpg. Couldn't be happier. On, one other probably important fact, both vehicles had/have similar style tires, that is LT type tires, not off road type. My mpg around the suburban area I live in is similar to yours, 14.5-15.5 mpg. Almost forgot, I think a lot of RAM owners purchase for the "hemi experience". I did not, because I was never purchased or owned a vehicle because of that kind of factor. That being said, I now get it, this truck does have a "little attitude", right from the factory, not after adding a bunch of after market stuff.