Your tow rating with EITHER engine will depend on how you equip your truck.F150 has a maximum trailer weight of 11,500 lb. and may be as low as you describe in your post, it's completely up to you. The so called 80% rule is complete nonsense. The truck is perfectly capable of towing 100% of its ACTUAL rating. That means you have to do the work to find the true trailer size it can handle. For what it's worth, they don't MAKE a 24 footer that would tax your truck with EITHER engine choice. The ecoboost will type MUCH better in the mountains though because there is NO power loss due to elevation (just like with a diesel).
Good luck Skip
