All anti-freezes have enthenyl glycol as the "anti-freeze" additive, that doesn't wear out, the difference between the types is the anti-corrosion package that is very important because you have water under pressure and heat up against bare metal, that will make it corrode. Yea, there are propelyne glycol versions as well, those are NOT recommended for the Commander.
IAT- The old Green Anti-Freeze has Phosphates and Silicates to coat the metal in the cooling system to protect it from corrosion and fight off cavitation damage. Cavitation happens most on the water pump blades. It has to be used with pure as practical water (i.e. distilled water, NOT tap water) and must be changed every 2yr/30k miles. People didn't follow those maintenance procedures and soon the anti-corrosion was depleted causing corrosion and it would even form solids and gunk in the system.
OAT - Was designed as a long life anti-freeze that was tolerant to the minerals in tap water, as a fix for owners that did NOT properly maintain their vehicles. It doesn't coat the metal in the cooling system, it chemical reacts with the metal to make it form its own anti-corrosion layer on the surface, thus the anti-corrosion additives last much longer. They do NOT protect brass, bronze and copper in much older cooling systems.
DexCool - Is GM's version of OAT that uses a chemical in the anti-corrosion package that is troublesome with certain plastics and seals, and when mixed with other anti-freezes. Most vehicles in the last 20 years no longer have the metals/plastics/seals that are incompatible with DexCool. And Dexcool has been improved over the years so that it is no longer the nightmare it once was when it was first introduced. But you would NEVER want to use it (or any OAT) in an old classic car that has materials that incompatible or unprotected by its ingredients or mix it with other types of anti-freeze.
HOAT - Mercedes/Chrysler/Fords Hybrid anti-freeze using a little of both OAT and IAT protection package. It has chemicals that react with the surface of the metals, it also has silicates to coat metals as well. It can do a better job at protecting a water pump. It can mix with IAT easily (but you have to go with the IAT shorter change interval) and is tolerant of mixing with a little bit of OAT anti-freeze, except Dexcool. It has a long change interval, but NOT as long as OAT anti-freeze. Zerex G-05 is the aftermarket equivalent, and its dyed the FORD amber color, Chrysler/Mercedes was Pink-Orange.
IAT and HOAT start coating right away and prevent corrosion right away, OAT/Dexcool take 5k-10k miles before they have fully reacted with all the metal surfaces and have it fully protected. As well, if there are air bubbles in the cooling system, oat can't react with the surface and protect it where there is air, and corrosion starts.
Water Pumps, suffer cavitation that will erode the impeller blades on the pump, OAT and DexCool has NO additives to combat that erosion. Engines that OAT and DexCool are recommended for have had a lot of development down to reduce the cavitation the water pump suffers, so that it can last without the additives it needs, like the old IAT and HOAT anti-freezes have.
Yes, you have a right to complain if a shop put Dexcool in your Commander, they did it wrong, simple enough. Keep in mind, the Commander doesn't have any metals/plastics or seals that are incompatible with DexCool. If the system was properly drained and flushed before being refilled with DexCool, likely the only thing was a little less protection of erosion on the water pump fins, and that's it.
The Commander engines have a reputation for the water pumps developing leaks, I wouldn't be so sure someone adding dexcool to the cooling system was responsible. If you have other problems that come with adding Dexcool, like lots of rust, solids, gunks or congealing in the cooling system as well as a water pump leak, you may have a case. If the Dexcool has been in there for years, you pull the water pump and find its all eroded away and out of balance, you might have an argument the Dexcool was behind the leak/damage. Quite frankly, if you properly switch a Commander to Dexcool, you'd likely NOT have any problems, but the recommended HOAT anti-freeze is better and that is why you should use it. I'm just warning you that just because there was a switch to dexcool, that doesn't guarantee its the source of your water pump leak, especially when a commander with the proper HOAT change at the right interval develops water pump leaks at the same mileage.
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