#2 Hi Sulfur diesel is used for off road diesel and home heating oil. You can get #2 hsd in two different sulfur amounts, 1500ppm and 500ppm. The 1500ppm has more lubrication than the 500ppm. Both can be used with no problems as HHO or off road diesel fuel. There is also low sulfur and ultra low sulfer DYED fuel that is available. These particular fuels burn cleaner but do not put out the btu or lubrication that the hi sulfur fuels do.
Sales tax is applied to all dyed fuels unless you are exempt (farming, horticulture, etc.) HHO is not exempt from sales tax, at least in Ohio that is.
As mentioned before, up to a b20 bio fuel blend will burn just fine. I know there is higher percentages out there being used, just depends on system. Using bio will clean the system if dirty. The bio acts as a solvent and a lubricator. It is a great thing once system is cleaned, but prepare to go thru a few filters until the process is complete.
They are coming out with different sulfur contents all the time with this stuff. I may have missed a couple.
I'm no expert, but I have bought, sold, handled, and delivered several million gallons of this stuff the last 12 years