Glad I didn’t farm! :)
Farmers didn’t have to pay the road tax on their fuel, while if you used it to drive to town in your diesel pickup, you would have to pay it.
Most ranchers/farmers would have a 500-2000 gal tank for their equipment to run their tractors and combines’. Frequently, they would just top off their pickup from the same stock tank.
Periodically, the Dept of Public Safety or county would set up road blocks on rural farm roads and stop the pickups, and would run a dipstick in the gas tanks to see if they were using the right fuel on the roadway.
If they were using red diesel, they’d have to pay fine for not having paid the road tax, and the dispenser would have to pay .20/gal for not abiding by the Road Tax.