Ram towing mileage

So I bought a 6x12 single axle enclosed cargo trailer for general use, and sometimes going to swap meets. I have a 2008 Ram 1500, 5.7L that I tow it with, and it's killing me on gas mileage. I would assume newer models would get at least somewhat better mileage than the 08. The last tow was in April, trailer only about half loaded, running A/C all the way, and it got 8-10 mpg. Do any of you have Rams that you tow a similar trailer with, and if so, what year model, engine, etc. Looking for some type of solution. Thanks in advance for the help.

Dustertogo