I've been doing a whole lot of research on Dex-Cool and trying to determine if I want to leave this coolant in my Northstar or pull it out and replace with something like Zerex G05 or Peak Global.
Apparently DexCool can become acidic over time if it is either a) not maintained, or b) exposed to air due to minor leaks in the coolant system. Over time, the acidity of the Dex-Cool can damage all kinds of gaskets. A number of folks who regularly replace head gaskets in Northstars have reported that the condition of the gaskets pulled from cars still running Dex-Cool often appear to be more worn out and rusty than typically seen with cars not running Dex-Cool. One person who has described this pattern is Jake (97EldoCoupe).
Now, we already know for sure that Dex-Cool can severely damage gaskets that have a Nylon carrier. The best description of this I've seen to date is here:
Also, although nobody knows for sure, the failure mode of our Northstar engine gaskets "may" be in part due to Dex-Cool becoming acidic over time. From what I have read on this message board, one of the more likely theoretical failure sequences could work something like this:
Step 1: the head gasket begins to slightly leak such that coolant makes its way to the head bolts
Step 2: the Dex-Cool is now exposed to air and quickly becomes highly acidic
Step 3: the head bolts start to become loose as the acidic Dex-Cool reacts with the aluminum block and dissolves the aluminum threads in the block
Step 4: combustion pressure places enough force on the bolts that they pull loose from the block due to the weak threads damaged by the Dex-Cool
Why does this happen with Dex-Cool? It appears that the addition of a specific organic chemical called 2-ethyl-hexanoic acid may be a big part of the root cause. As far as I can tell, ONLY GM and ONLY Dex-Cool (and Dex-Cool clones) use this organic acid in the design of the coolant. Ford tested Dex-Cool in one of its vehicles and decided NOT to use Dex-Cool, instead moving toward a Hybrid coolant containing organic additives (but not 2-ethyl-hexanoic acid) while still containing low levels of silicates (like the old green coolants had). A good primer on the various coolant options can be found here:
I realize that some people are die-hard Dex-Cool supporters and others either want to know what their options are (besides Dex-Cool) and/or would like to switch from Dex-Cool to some other coolant which may avoid some of the issues with Dex-Cool. I do not want to start a "flame war" but rather have a meaningful dialog about options besides Dex-Cool for those of us who are interested.
One of the best coolant cross reference matrixes I've found so far is here:
This .pdf is also attached to this post.
From my research, for anyone who wants to convert from Dex-Cool or a Dex-Cool clone and who also wants to avoid the 2-ethyl-hexanoic acid, I think there are a few options: Zerex G05 (does contain some silicates as well as borates), Peak Global (does not contain silicates, phosphates or borates), Motorcraft Orange (G05 clone), Honda Blue (contains phosphates by no silicates or borates). There may be others as well.
For myself, I've converted one of my two Northstar powered vehicles over to G05 and I may use Peak Global in the other . . .