Im an RV Transporter
I have a 38 gallon main and a 98 gallon aux.
ULSD results in (to me) much lower miles per gallon. When you're only getting paid $1.08 a mile and fuel takes up 37 cents of that (10 mpg loaded), there ain't much left over for maintenance, loan payments and insurance. And since we don't get paid for the trip home, take another 25 cents out of that $1.08 (16 mpg) for the ride back.
When you consider everything in this country gets delivered by diesel trucks at some point, then it's easy to understand why the economy is beginning to tank.