I have always used prestone green and distilled or RO water. It has always worked well. I was doing some coolant research and peak has a product called fleet charge. It is a pink coolant with anti cavitation additives. It looks like pretty good stuff. it Is speced to work with the 6.9 and 7.3 engines. I have replaced many 6.5 water pumps and I have always seen cavitation damage on the timing cover. What do you all think of this stuff? Would it help/hurt in a 6.5L diesel? It claims to have 8% better thermal conductivity. I am about to replace my radiator in my 93 and I am thinking of flushing and replacing with fleet charge.