I have owned a few 6.0L's and always used the fuel additive. Now that you mention coolant additive I think I recall that without it (or proper ooolant) you can get destructive cavitation.
patperry2766 wrote:
Diesel fuel additive
This is something else I suggested to him to research.Though this article is dated, there are several others out there. Since I don't own a diesel, I can't validate the opinions expressed, but it does seem to make sense in the fact that the 7.3 was designed to run on a different fuel blend than the ULSD that is only available today.
Maybe someone who has direct knowledge and experience can elaborate more.