Got to agree with most of the other posters. We went to the Black hills the week of July 4th in 2014. Going west on I-90 we ran into an absolutely brutal headwind. Thankfully, we didn't take the camper with us on that trip. Don't know if that kind of wind is common or not there, but the many RV's that we did see were really struggling. They were swaying all over the place and struggling to stay in one lane. Just based on that, I would definitely take the diesel truck if it were me. Enjoy your trip, we loved it there.