This statement......
"So…..The Diesel returned roughly 20% better MPG……but diesel fuel costs roughly 20% more…..so cost wise, it’s a wash."
Is not correct. 20% of two different numbers are not the same.
You did say your diesel was always 12-13 mpg no matter what. So lets say 12.5 mpg which if you deduct 20% brings you to 10 mpg. You state that your average was 9.34 mpg on your trip which is 25% less than 12.5.
You didn't state how much regular fuel was but according to gasbuddy it is around $2.90 in that region. That makes diesel $.58 cents higher at 20% which comes to $3.48. I very seriously doubt that it was this much of a difference especially since gas buddy shows $3.20 for diesel, but we will run with it.
So using these numbers with your diesel being at 12.5 mpg and your 6.4L at 9.34 mpg and gas being $2.90 with diesel being $.58 cents higher (again, I doubt this) at $3.48, the diesel would still come out cheaper over the course of your 2,700 mile trip by over $85 which is about the cost of another full-up. If you use the $3.20 cost for diesel that gas buddy states, then it would be a $147 difference.
The OP towed a 4700 pound trailer. That is nothing for either a gas or diesel engine. While the gas probably knows the trailer is behind the truck, the diesel does not even feel it.
Having said that, your analysis is correct but how can the OP not want to brag about his new truck? While the 6.4 is a very capable gas engine, it is not in the diesel league and to compare is probably not really proving anything nor statistically meaningful. But he has a new truck and that is always exciting.
