#1 and #2 Diesel Fuel are the primary fuel types for mobile and fixed diesel engine applications.
When buying fuel, #1 is often labeled at the pump as "Premium Diesel" or with a Cetane number of 44 or 45. It is thinner and a better choice in the winter.
#2 Diesel Fuel is thicker. Since it is thicker, it has more lubricating properties. Diesel #2 Fuel will gell easier in cold weather. This makes starting harder. It can also cause rough-running.
#2 Diesel is often labeled at the pump with a Cetane Number of 40
Home Heating Oil is NOT #2 Diesel oil. It is very close. It may have the same in ignition quality and lubricating ability only. Refiners do not intend Home Heating Oil to be used in an internal combustion engine. Fuel that is intended to be burned in your furnace, may not have the smoke suppressants, ignition accelerators and biocides to kill fungi and bacteria that is generally are present in the Diesel Fuel at the pump. The ones that Automotive vehicles use.