Tanks are ~100-120 gallon range. The rigs, fully loaded get anywhere from 6-12 mpg depending upon load, horsepower and terrain.

Now, as far as getting Diesel, who do you suppose transports this Diesel to/from various areas? I would guess Truck Stops would ask for more, and as they are a customer, if Supplier A won't deliver, then competition from Suppliers B-Z will.

And that Diesel will be hauled by a fellow truck driver.