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Unread 09-08-2012, 03:12 PM   #1
JackAndCoke
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Coolant type - HOAT necessary?

Plan on flushing my rad this weekend. A friend of mine tells me to use any green coolant, but my online research suggests I only use the Zerex G-05 with HOAT additive with distilled water.

What the general consensus?

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Unread 09-08-2012, 05:12 PM   #2
metalhead
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From what I have read you need to use the g-05 on 2001 and up chrysler,jeep,dodge vehicles.
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Unread 09-08-2012, 05:35 PM   #3
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Yes.. that's it or right from Chrysler..I found Napa was the only place to find the zerex
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Unread 09-08-2012, 06:05 PM   #4
hamilton5
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omfg another coolant thread... GREAT

THANKS FOR USING THE SEARCH JackAndCoke ALLOW ME TO SHANK YOU
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Unread 09-08-2012, 06:26 PM   #5
rm2001wj
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Quote:
Originally Posted by metalhead View Post
From what I have read you need to use the g-05 on 2001 and up chrysler,jeep,dodge vehicles.
Even the 2001 came from the factory with the green stuff; at least mine did. Certainly don't need to use HOAT in a 99.
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Unread 09-08-2012, 06:42 PM   #6
tjkj2002
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Originally Posted by rm2001wj View Post
Even the 2001 came from the factory with the green stuff; at least mine did. Certainly don't need to use HOAT in a 99.
The one thing is though what you don't know is that coolant color means nothing.What everyone thinks is "the old green stuff" is Ethylene Glycol(AIT coolant) and virtually impossible to find these days.

The green coolant you find at parts stores these days is OAT coolant or better known by GM's trademark name Dexcool which is not to be used in your cooling system.Can not mix OAT coolant and HOAT coolants unless you like sludge.
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Unread 09-08-2012, 06:58 PM   #7
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What Ive read about HOAT is that it is a Hybrid OAT. Which means it has some parts from OAT and some parts from conventional formulas making it compatible with both. OAT is NOT compatible with conventional, but HOAT is. The biggest thing to remember with antifreeze, is that HOAT and OAT break down after about 5 years. Conventional formulas break down after about 2 years. So regardless of the type you use, follow the service interval meant for that type.
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Unread 09-08-2012, 07:24 PM   #8
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Originally Posted by ezflip View Post
What Ive read about HOAT is that it is a Hybrid OAT. Which means it has some parts from OAT and some parts from conventional formulas making it compatible with both. OAT is NOT compatible with conventional, but HOAT is. The biggest thing to remember with antifreeze, is that HOAT and OAT break down after about 5 years. Conventional formulas break down after about 2 years. So regardless of the type you use, follow the service interval meant for that type.
Both OAT and HOAT coolants are AIT coolant based.OAT coolant and HOAT coolant can not be mixed,OAT coolant also does not like mixing with AIT coolant but HOAT coolant will since AIT and HOAT coolants both have silicates while OAT coolants do not.
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Unread 09-08-2012, 07:28 PM   #9
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Originally Posted by tjkj2002 View Post
Both OAT and HOAT coolants are AIT coolant based.OAT coolant and HOAT coolant can not be mixed,OAT coolant also does not like mixing with AIT coolant but HOAT coolant will since AIT and HOAT coolants both have silicates while OAT coolants do not.
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The third type of antifreeze on the market today is the hybrid OAT, known as HOAT (or G O-5). One of the primary problems with OAT formulations is that they are not compatible with conventional antifreezes. The chemicals used in OAT antifreeze react to some extent with some of the inorganic salts and other components in conventional antifreeze. The result of this interaction is the generation of cloudiness and precipitates. HOAT formulations are called hybrid because the additive package contains ingredients from both OAT and conventional formulas and is compatible with both.
Hybrid OAT antifreezes provide both fast acting and extended life corrosion protection, eliminate the problem of anti- freeze compatibility, and therefore are compatible with all types and colors of antifreeze.
recycool.com
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Unread 09-08-2012, 09:14 PM   #10
tjkj2002
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Originally Posted by ezflip View Post
They don't know alot about HOAT coolants.You can not mix HOAT and OAT,forms sludge.You can use HOAT coolant in a cooling system designed for OAT coolant but not a good idea to use OAT coolant in a cooling system designed for HOAT coolant,of course after a complete flush.
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Unread 08-18-2013, 08:01 PM   #11
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Originally Posted by tjkj2002 View Post
They don't know alot about HOAT coolants.You can not mix HOAT and OAT,forms sludge.You can use HOAT coolant in a cooling system designed for OAT coolant but not a good idea to use OAT coolant in a cooling system designed for HOAT coolant,of course after a complete flush.
Does anyone have any more information about the differences in components of a HOAT cooling system vs those of a OAT system?

I'm going to do a complete flush in my 06 LJ since I have no idea what's in there now, and I'd really like to use OAT coolant if it won't harm anything. It's cheaper, much easier to find, and more likely that someone else on the trail would have a bottle of OAT if I ever needed to add coolant for some reason.
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Unread 08-18-2013, 08:28 PM   #12
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FWIW, I ran green after the rebuild, and then Autozone "Universal" after a water pump replacement.

Running Mopar coolant 60/40 with water, and I'm about 15 degrees cooler running now.

Use Mopar coolant. The reason it was changed in 2001 was because of the mistake of using Green. The Mopar coolant isn't that much more expensive, and will work best for you.
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Unread 08-19-2013, 12:04 AM   #13
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Another coolant thread? LOL.

Just put Zerex G-05 or Mopar coolant in your Jeep and don't look back. And, don't worry about it.

I have a 2000 model year Jeep and I use HOAT, no issues.
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Unread 08-19-2013, 02:09 AM   #14
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I like to use lime koolaid
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Unread 08-19-2013, 06:13 AM   #15
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The decision to use Hoat was made when Daimler-Benz bought into Chrylser. It is fine for newer non-ferrous metals such as aluminum and closed (non-vented cooling systems. The main reasons for OAT & HOAT coolants was for manufactures to make the claim of "5 year maintenance free". On the old iron 4.0 the best coolant for rust protection is the OLD IAT (ethyl glycol,silicate coolant as long as it is changed every 2 years. There is no advantage what-so-ever of using HOAT in the 4.0. HOAT does a poor job of protecting iron and once it starts to break down it turns into the most nasty,acidic mess that you could possibly put into a coolant system. Silicate anti-freeze has been used for over a century without any problems and nothing protects ferrous iron better than silicates...,period.
All the brown sludge,corrosive gasket eating and overheating problems did not evolve until the introduction of organic coolants. IMO once the engine is out of warranty or past 5 years I flush (throughly) and switch to the old conventional IAT. After that I change every two years with the satisfaction of seeing nice green coolant and not HOAT mud.
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