Just finished a 500 mile trip over mountain passes and across desert towing my Rockwood 2612 ws. (6800 lbs loaded)- 36 mph winds and >100 ft visibility for a while! (fires and dust) 13.2 mpg
Had no issues!
After you do your reading on the forum and other research you will probably decide a tune is in your best interest. These can be really great trucks but many have ben unhappy
I have only heard of a couple people adding an oil cooler although some might say during towing duty heat is a problem.
Most here would agree that the EGR system is the weak link and needs to be deleted through a tune or a full delete.
Both are talked about extensively on this site!
if you want to drive it and be happy with it you should tune it. the tune can be taken out and reinstalled at will for warranty work.
most are unhappy with the truck in stock form. very few owners are unhappy with tuned versions!