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!