I've never used fuel additives other than a stabilizer for my stored gasoline.
The only things the diesel additives do for sure is make the user feel good and lighten their wallet.
I was a heavy equipment tech for a number of years. None of the two dealerships I worked for stocked or sold additives. They just told their customers to use clean dry diesel fuel. Also, time purchases of fuel such that you got the winter blends (suppliers add anti-gel for you!) in cold climates to prevent gelling. In Michigan, the winter blends come on line about late October.
Oh, and don't ask the poor clerk behind the register at the fuel station/convenience store if the winter blends are out, they won't have a clue. Just look up the area distributer on line and check or give them a call.