I think our class B campervan is about 11k loaded and the V10 does great. I think a new truck/trailer combo would go a bit bigger—13 or 14K for the combined total.
My hunch is that if you look at the total picture the costs of diesel get prohibitive. Suppose the gas truck is $65K and the diesel is $75K. For comparison’s sake, invest that $10K difference in stocks or whatever. After X years of ownership, bring that $10K component back on the spreadsheet. But also if the reverence for diesel is so great, the resale value will be better than gas. Go into all the operating costs, including oil changes, scheduled maintenance, etc and see.
Here’s a video comparing the F150 Hybrid vs. a Jeep diesel.
video
At the end, they say the Ford got 8.1 mpg towing, 29.9 mpg empty.
The Jeep got 11.5 mpg towing and 21.1 mpg empty.
As I said, my plan would be to tow a few hours, then set up, park, stay a couple weeks.
But the two vehicle would be used for getting around, so both figures (towing and empty) matter. And here’s an article talking about whether diesel merits the extra cost. Pretty good article, has some historic trends and comparisons.
Fifteen years ago, the government premium paid for the diesel option ranged from $2,200 to $3,000. Today, that premium has risen to about $8,000.
Horses for courses, naturally…