Howdy,
Way to many internet rumors flying around.
A fuel depot terminal with a 1,000,000 gallon tank with 15ppm ULSD pumps 8,000 gallons into a tanker truck. The tanker truck takes it back to its own company distribution tanks. A delivery truck fills up with 3,000 gallons. That truck is going out to delivery... heating fuel oil, off-road fuel tanks. They add a red dye to show the product is not road taxed. (People from Washington do not need to make comments about tax)
By today, May 2018, all diesel fuel being sold in public consumption is 15ppm ULSD.
HHO = home heating oil = can be different. If there was some kind of kerosene that dropped to 20 cents a gallon, then a separate tank would be dyed and delivered for home heating.
15ppm ULSD needs to meet certain specs. It has lubricity modifiers, low smoke additives, etc...
HHO does not need these things. It could have a higher amount of kerosene etc..
The fuel terminal would have to keep separate stock of many flavors. It was found to be easier to keep 1 product and add the red dye for final delivery use.
Original topic.
Off-road diesel is just that. Off-road vehicles. Tractors.
Around here the D.O.T. inspectors will do checks around livestock sale barns.