I was wondering the same thing? I replaced my waterpump last summer and used the Prestone ELC (the truck had green in it already) and added a bottle of Napa Kool into it. When I did this I noticed a clear like scum form on the inside of the degas bottle.
After reading on here I don't think that was a good thing.
I searched around at my International dealer and a few heavy duty truck supply stores but couldn't find a heavy duty concentrate antifreeze with the SCA in it. They all only carry premix. I finally did find one at Napa called Fleet Charge, SCA Precharged, that seems to meet all the requirements for SCA, Low Silicate, Nitrite, etc. I drained the rad. and block, flushed all that scum out refilled with deionized water and have had no problems since.
Just my experience with it.