I am the guy that started a conversation on a different thread as whether to use straight coolant in the WJ v8 or the 50/50 mix. In my seemingly never ending quest to understand newer vehicle technology I found a thread on another Jeep site regarding regular coolant vs. HOAT coolant. Up until now I knew that there were different types. But I didn't know that these Jeeps should only use the HOAT type. The write up suggests that not using the HOAT type will cause cooling system failures, which may have been the cause of my heater core failure and not the mix or lack of mix of standard coolant. Other sites tend to support this.

So I am asking here what is the requirement for these engines? And despite what that might be, what are most people using this forum putting in their Jeeps? Is using the recommended coolant as critical as it is made out to be? And since the coolant that the mechanic who replaced my core put the green stuff back in. Should I change it out?

 

If you have the 2000 that's in your signature, you should use ethylene glycol (Green) coolant. Chrysler went to HOAT in 2001 and newer. If you want to go to HOAT, you MUST flush ALL of the glycol out of the system, even what's in the heater and block. HOAT is supposed to perform better in systems with aluminum components like radiators and cylinder heads. It's an organic coolant and better for the environment. That right there makes me cringe.

People have complained about HOAT breaking down and forming sludge in cooling systems. Dex-Kool was designed for the same reason and stinks as well, AND it's not the same as HOAT.

At one time, Honda started using a red coolant, commonly known as Asian Coolant. IDK anything about it and I really don't care either.

IMHO, green ethylene glycol has worked well in any vehicle for over 100 years so I'll keep using it.

The whole point is, water is the best for heat absorption, but needs to have anti-freeze components in it and corrosion protection additives.

 

Thanks again Dave. If by "signature" you mean "profile" . It does say 2000 Grand Cherokee.
I did find the information about the change over to HOAT in 2001 by Chrysler in another place on the web. And thanks for letting me know that I have to thoroughly remove all the PG to change types. I wasn't clear about that.