GM's specs were all screwed up, that is why the Dexcool has been reformulated some 6+ times, why there have been several lawsuits over it, and why so many GM cars had so many troubles.
The newer specs are certainly better, and the newest stuff you buy in the store is probably better as well, but just because both VW and GM spec a HOAT coolant package does not mean they are the same, just like the high-end Behr paint you buy at a home center is better than the cheap stuff you buy at Wal-mart, yet both can be a white latex paint.
It is old knowledge that GM's specs were 'looser' and they did not get the additive package correct (GM themselves confirmed this). This allowed the additives to come out of suspension when exposed to air, and caused all sorts of gunking as well as damage to the non-metal parts of the cooling system, which on many GM engines was the intake gaskets themselves. Trust me, everyone working on cars for the last 15 years has all-too-often seen this damage.
Volkswagen water-cooled cars (except the Vanagon) all use a sealed cooling system; there is no 'overflow' bottle, merely the expansion tank. So technically, the coolant should never come exposed to air anyways, since the pressure release on the cap is just for an over-pressure protection, there is never any migration of coolant in and out of the pressurized part of the system like many (most) GM cars had.
So, was it all the Dexcool spec's fault that all these GM cars had trouble, or was it just the old-fashioned cooling system designs that did not play well with HOAT? Probably a little of both, however I have seen similar gunkiness in VAG products when Dexcool has been used, but I think some of that may have been from a coolant mix. I do not think Dexcool mixes well with G12, despite both being HOATs, and this can cause some issues by itself.
I think it silly to whine about what ends up being a few pennies per year owned to use the proven correct stuff that NEVER seems to gunk up at all, has never caused any class-action lawsuits, and has only been reformulated a couple times, once for some reverse-compatibility with G11 (the blue stuff, which is STILL in use by BMW and MB on many models).
For anyone that has a Dexcool problem, Permatex makes some excellent flush stuff that will clean the crud out (of a Volkswagen or a GM product
) . The only caveat is that it is pretty harsh stuff, so if you run across a rotten gasket or something, it WILL exploit that failure as often the crud and gunk is the only thing left holding it together. I have used it with great success to clean stuff like this:
Funny, if you look in the cooling systems of newer GM vehicles, you will actually see the newest stuff they use is pinkish, just like G12, not the orange-salmon color the Dexcool once was. I'd bet the newest stuff from the factory is very much like what Volkswagen already knew works.
