Additives...
Whether it's fuels or lubricants the diesel mechanic that conducts engine and systems classes at our YC always tells owners to
first follow the manufacturer's recommendations. With four + decades of experience his take on it is that the engine/transmission engineers have a lot of R&D experience that owners need to take advantage of; and the engine builders have millions of hours of service time to guide them.
As you might imagine, he advises against putting anything other than some bug killer in the fuel. That, and doing your best to put clean dry diesel into the tank (and keep it that way).
This often disappoints owners who are always asking about some new (or old) "special super panther-piss" additive for their engines...
Cheers,
Loren