We move a a lot of Stanadyne Performance Formula. It’s has everything you’d want and only adds about 10-12 cents per gallon to fuel cost. Most guys find they get enough mileage improvement using it to more than pay for it.
Amazing stuff for sure.
Have used this for about 100k it is worth four times the cost or at least it is in the '06 6.0, 178k original injectors dilution just about where it was when new-in an E450 rv the engine is derated to about 140 hp depending on who you speak with. Fortunately I am not too far from a D&W diesel store where the cost is about 20% less than the best online offers, or it was when I picked up a case in July of '22 of the 16 oz bottle (the size that treats 60 gallons); the fuel and oil filters are even a better deal.
Don't know if the additive is compatible with the def engines.