2018 Ram fuel milage questions

I have a 2017 ram 1500 hemi quad cab with 3.21 gears. I get 22-23 mpg on highway. I am thinking on trading it up to a 2018 long horn or harvest model and they all seem to come with 3.92 gears. Almost all of my driving is highway. What do you get with the 3.92 gears on the highway? I did put a k&n filter in mine, otherwise stock. Can I expect a drop in milage or stay the same? I want to get as much info before getting another truck.
Thanks, Paul