Originally Posted by 440Magnum
Originally Posted by StevieC
HOAT = Hybrid Organic Acid Technology. It contains IAT and OAT.
OAT = Organic Acid Technology. It does not contain IAT.
That is the difference. HOAT LITERALLY CONTAINS OAT!
OK, I'm not even saying this for you because you obviously refuse to see the forest for the trees... but for anyone else reading this: NOT TRUE. Its like saying "sodium hypochlorite and ammonia are both disinfectants, so I can mix them and nothing will happen" (hint... don't do that unless you're wearing a breathing apparatus).
"OAT" is not a chemical, its a category of chemicals, called organic acids. There are many, many, different possible organic acids that can be used in cooling systems, and while they all work in a similar way to inhibit corrosion, each different organic acid can have OTHER chemical properties that can be vastly different from one to another. A classic example of this is the organic acid used in DexCool, 2-ethylhexanoate. Its a great corrosion inhibitor, but it has a softening effect on certain gasket materials that can cause them to fail. Engines using 2EHA have to be designed so that they don't use those plastics. On the other hand, the organic acid in G-05 does not attack plastics. Both are organic acids, but react differently when exposed to other chemicals.
It is true that HOATs contain both an organic acid and inorganic components. But they always contain organic acids that are CHOSEN to be compatible with those inorganic components. An OAT has no such restriction- since its meant to be used without inorganics, the organic acid needn't be compatible with any inorganic additives. When you add a random OAT to a HOAT, you are now bringing a DIFFERENT organic acid into the mixture, and it may react violently with a) the inorganic components of the HOAT, b) the other organic acid that is used in the OAT, or c) both.
That is absolutely, unequivocally, clearly what is happening when you mix the two Mopar P/N coolants based on the TSB that was linked. The ammonia smell would indicate that the organic acid in the OAT is likely reacting with the nitrites in the G-05 HOAT (ammonia is NH3, after all), but it could be any number of reactions or sequence of reactions involved.
Excellent post and sums the risks here up clearly.