Just so i am clear, we use g-05 coolant. That is what comes in our systems from the Assembly line. g-05, be it ford, chrysler, merc, or zerex, is all the same. G-05 is a PG coolant that is precharged with sca's for cavitation prevention.
g-05 is an acceptable coolant for wet lined diesel engines, if it is replaced frequently. It is not the best choice. a ELC would be the best choice.
Adding a SCA to g-05 is not harmful at all. Ford recommends the use of SCA's to it's "ford gold" (g-05) coolant for many f- series. Deere and Caterpillar also recommend the use of sca's in their g-05's for some applications. Point is it does not turn to snot. It is, however, so much easier to frequently replace g-05 in our situation that it is to attempt to maintain the sca.
Some info on g-05
http://www.whitfieldoil.com/www/docs/16 ... reeze.html
http://www.shamrockchicago.com/MSDSZerex-G-05Af.pdf
g-05 is an excellent coolant. BUT elc's are better!
Delo ELC, Rotella ELC, International's Fleetrite ELC, CAT ELC, Mobil 1 ELC
etc etc, are all excellent. The biggest advantage over g-05 is the long term stability, literally a life time fill for our crd's, if flushed properly.
Also it has better heat transfer over g-05. What it lacks is in freeze protection. 50-50 g-05 has a -34f protection and typical 50-50 elc's are -36.5F. You may say, hey no problem there, but think about it.
g-05 at it's highest recommended mixture protects down to -90F (70%)
ELC'S are usually around -60F at their max (60%)
I use g-05. There's noting wrong with it.
For the record duramax (isuzu), cummins and ford (international) light duty diesel engines used in 2500+ trucks, are all parent bore.
Earlier i said that i flushed my g-05 with new g-05 every oil change, this is true for the last 3 oil changes, because at 30k i flushed my coolant with go5, witch is clear-yellow, and the mopar g-05 is red, my coolant is somewhere in the yellow-orange zone, indicating to me that i need to continue to replace it.
g-05 is fine.
adding sca' to g-05 is ok, but i'd just flush it. And you better not do it without measuring the content.
Elc's ARE better.
One of these days when i feel like flushing with water, the viscous heater, and the heater core, i will use a elc.