Originally Posted By: onion
Originally Posted By: Drew99GT
Why does my Decool not turn to sludge onion?
Because you're lucky?
I was similarly lucky when I bought an '01 Lumina with 159K a few years ago. The Dexcool was a nice, transluscent red... and the cooling system was squeaky clean. In my experience, Dexcool works very well- in those cases where it does not turn to sludge.
However, I've seen dozens of GM's in which the Dexcool has turned into a mud-colored sludge. If you don't believe me, just do a yahoo image search on "dexsludge". Look up the GM class action lawsuit over Dexcool. Go down to your local used car dealer, and check out a dozen GM's over 5 years old with at least 80k miles... half of them will be sludged. That's been my experience.
There are lots of theories out there as to why Dexcool turns to sludge. The most common (and I think likely the most correct) theory is that this sludge forms when air is introduced into the cooling system. Some nimrods even go so far as to call this proof that Dexcool isn't the problem.
And I'll agree with them in that under PERFECT conditions, Dexcool works very well. But real life is rarely perfect. Introduce air from an otherwise undetectable leak, overheat the system a couple times, or dare to mix in anything else that isn't Dexcool... and your cooling system will quickly look like this one.
http://www.sancarlosradiator.com/images/dexmud31.jpg
And while I'll readily agree that none of the aforementioned adverse conditions are Dexcools "fault", I've never heard of any other coolant congealing into this nasty form of sludge- only Dexcool. And since alternatives exist that WON'T turn into sludge at the first minor imperfection in your cooling system... I really don't understand why any informed consumer would knowingly put that GM Kool-aide into their vehicle.
Personally, I prefer G-05. It's a bit harder to find than Dexcool or the universal coolants (which are basically yellow dexcool), but it's a long-life coolant with all the benefits of dexcool and none of the drawbacks. It's a HOAT coolant, using a different OAT additive than Dexcool (or universals) and also a small amount of silicate (hence that "H" for 'hybrid'). It lasts as long as dexcool, doesn't attack polymer seals like dexcool, cools just as well, and best of all- doesn't turn to sludge.
Ford and Mopar have used G-05 in their vehicles for years, without even a fraction of GM's cooling system troubles.
And for what it's worth, every "all-makes" coolant that I've investigated (including Prestone and Super-Tech) uses the same OAT additive as Dexcool. I.e., it's similar enough that I personally wouldn't use it- not when a better alternative is readily available.
It's got to be something more than air because I successfully ran Dex Cool for years in a car with one of those pressurized overflow tanks where there is air in it.
What I suspect is causing the sludge is that when the cooling system depressurizes after cooling off, it sucks in a small amount of motor oil and then that oil gets whipped up into a sludge when the car is running.
