A lot of people think they must have a diesel to pull big trailers but that is not necessarily the case for everyone. We made a similar trip in August..Up thru North Dakota (Roosevelt National Park), on over to Glacier and down to Tetons then back home. 5400 miles and our 2021 Ford F250 with the new 7.3 gas engine did a fantastic job.Overall MPG which included some day trips without pulling our 31' 5th wheel was 10.75. New diesels are a pain due to EPA restrictions. I think anyone pulling over 12K could use a diesel but not everyone is doing that.