Many have gone away from Propylene glycol due to sludge issues cause by air getting in to the system. GM silently switched back to Ethylene in the Dexicool for that reason.
Propylene has lost a lot of faith due to sludging.

 

I don't disagree with you on the sludging with the 1st gen Dexcool. Some folks probably mixed the old Silicate Phosphate formulations with it. I haven't had problems with my 2000 C2500 Classic with the L65 6.5 or my LS4 5.3L Impala but I've been careful to not mix antifreeze types. Dexcool is OAT.

The latest and greatest Polaris coolant is Yellow. Yellow is usually HOAT but not necessarily. The MSDS says it contains a proprietary blend of Organic Acid Salts so it's not IAT. http://polaris.hs.llnwd.net/o40/lub/...0_05302015.pdf


I have a mix of oddballs. I don't like mixing coolant types if I don't have to. Probably not necessary to worry but no need to buy trouble. Most published info says it's not a good idea to mix flavors of acid tech IAT, OAT and HOAT coolants and never to mix the acid tech with silicates.

I always use pre-mix because it's easy. Tap water has minerals in it and tends to be ionized right from the tap. Mixing with distilled water is just one more step and it takes a few thermal cycles to de-ionize it.

Both the Subarus use the 10 year blue Subaru coolant they shipped with and I'll keep using it after they get to 10 years unless some outfit makes a proven equivalent. Subaru head gaskets are fragile enough already.
My VW PD TDI uses the weird pink German G12 spec coolant but not the overpriced stuff from VW. G12 is a published VAG spec so there are some pretty reasonable alternatives.
The LS4 & L65 both use Orange OAT (Dexcool but not from GM).
The Pre 1990 cars trucks and tractors use the "Prestone" silicate and phosphate "Green".

 

All I know is that I've heard the horror tales of the old orange Dexcool for years,but that's what's been in the old Silverado since day one. I've had one water pump leak around one small o-ring against the block,replaced the pump and replaced with the same old orange Dexcool.That was years ago somewhere around 145,000 miles and it's getting close to the 275,000 mark now. Still has the original upper and lower radiator hoses.Luck may have a lot to do with,hoses may burst at any minute,but this has been the best old truck I've owned since an old Dakota I sold with over 252,000 miles to get the Chevy.

 

As long as you were out of earshot when you said it you'll get away with it...

That's been my experience with both of my GM engines that have Dexcool. My 2000 L65 6.5L blew out the water pump and thermostats around 110,000 miles so I flushed and re-filled it with Prestone Orange Dexcool 50:50 premix while I was getting dirty. She's over 250,000 miles now on the original PMD too. The 2009 LS4 5.3L has the factory Dexcool anti-freeze with a small top-up of that same Prestone Dexcool premix.

My best guess is those "Deathcool" tales are from the very beginning of the Dexcool rollout in the 1990's because some folks topped off with the green silicate stuff.

 

Parked in the garage,can't hear me.. Part of the longevity on both of them could have been that I drove 100 miles a day to get to work,a lot of it nonstop once I got to the Interstate. 9 years on the old Dakota, close to 11 on the old Silverado. That's another reason I'm glad I'm retired. Lot of long highways down here.

 

The new Dex is just fine, reformulated with ethylene glycol,new stuff is just fine. Mind you though, there are so many good altetnatives out there, the choices are endless!