OK now this may help.
I pay $3.619 per gallon of regular gas here in Arizona.
Diesel is running $4.019 which comes to a 40 cent more per gallon.
Now for diesels to break even they must get at least 10% better gas mileage than a gas.
So if I get 12 mpg pulling my 5th wheel with my gas engine the diesel must get at least 13.2 mpg pulling the same weight to break even.
Now look at the extra ost of the diesel to the gas engine. Typically $10,000 more.
So how many more miles can I drive my gas engine with $10,000?
At $3.619 I have 2,763 gallon of fuel that I can buy.
With that I can pull my trailer 33,156 more miles.
So this is why I bought a 6.2L gasser truck