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There seems to be some confusion between HOAT and OAT coolants. 2008-2012 Challengers use HOAT coolant. From 2013 to the present, all Challengers use OAT coolant.

Here is an explanation on how these coolants differ:

Hybrid organic additive technology (HOAT) which is orange in color. Manufactured for NAFTA, it uses a combination of organic additives (fully neutralized organic acids) and one or more inorganic materials; uses silicates as the fast acting anti-corrosion agent – FCA HOAT (MS-9769). It last for 5 years or 102,000 miles, whichever comes first.

HOAT-based antifreezes also contain an OAT additive package, plus an additional dose of silicates.The silicates are fast-acting chemicals that form a protective coating on aluminum surfaces. However, as the coolant ages, some of the silicates may drop out of solution.These particles can have an abrasive effect as they circulate in the cooling system, accelerating wear on water pump seals and plastic impellers, plastic radiator end tanks or inside metal heater cores with sharply curved tubes. To avoid these kinds of problems, most HOAT-based antifreezes use stabilizers to keep the silicates in solution, and they contain only a small amount of silicates.

• Organic additive technology (OAT) the factory fill on FCA products is purple in color – Contains only organic components, no inorganic materials – FCA OAT (MS-12106). It is a "permanent" coolant and lasts for 10 years or 150,000 miles, whichever comes first.

OAT-based antifreeze uses chemicals such as carboxylate, sebacate and 2-EHA (ethylhexanoic acid) to prevent corrosion. Antifreeze manufacturers won’t reveal the exact makeup of their OAT additive packages because they are proprietary secrets. But the chemicals are typically slow-acting so they can neutralize corrosion inside the engine, radiator and cooling system over a long period of time.

Caution: OAT coolant is not compatible with HOAT coolant - do not mix them!!! The corrosion inhibitors are different and can cause long term corrosion problems if mixed.

Other Cautions: There are several different OAT coolants available today, however they are not necessarily compatible. Using the correct coolant and water mixture is important for effective cooling. The recommended coolant mixture for most climates is 50% distilled or de-ionized water with 50% coolant. Do not use water with a high mineral content because:
• The inhibitors in the coolant can lose their efficiency and lower the coolant’s useful life.
• In addition, deposits can form inside the cooling system. These deposits reduce the ability of the cooling system to transfer heat. A 50/50 mix of ethylene glycol and distilled or de-ionized water provides the best mixture to prevent corrosion and obtains a freeze point of -37°C (-34°F).

Note: Never use HOAT coolant with a concentration greater than 60% coolant and 40% distilled water.

1024959
 

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How do you flush these modern radiators?

Back in the day I would install a fitting in the heater hose, attach a hose to it, turn the water on, start the car, turn on the heat and open the drain on the radiator and let the hose run until the water ran clear from the radiator.
 

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The Bacon Hauler (‘12 Cop Charger)
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One more important footnote in the HOAT vs OAT discussion is corrosion protection setup time, i.e. how long before the coolant establishes adequate corrosion protection on unprotected surfaces in the cooling system.

With HOAT, the onset time is immediate. Newly installed parts or freshly flushed/cleaned cooling systems will benefit from the HOAT coolant’s corrosion protection right away.

With OAT, there is a significant onset time, generally said to equate to about 5,000 miles of operation.
 

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The Bacon Hauler (‘12 Cop Charger)
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How do you flush these modern radiators?

Back in the day I would install a fitting in the heater hose, attach a hose to it, turn the water on, start the car, turn on the heat and open the drain on the radiator and let the hose run until the water ran clear from the radiator.
You can still use one of those heater hose T inserts, but coolant is circulating through the heater core regardless of HVAC settings, so no need to mess with the heater settings while doing all this.

Also, some folks shy away from that approach since it pretty much guarantees tap water will be left behind inside the coolant system to mix with the incoming fresh coolant/water mix. I’m not one of those worry-warts, but they are out there for sure.

Worrying about the adverse effects from mixing a pint or less of tap water with 15+ qts of coolant mixture is akin to circumcising a mosquito IMHO.

But hey, I’ve seen pictures of some of y’all’s garages on here, and I understand some of y’all’s mental state is such that it cannot even entertain the thought of filthy, dirty tap water mixing with your chase, pristine, virgin distilled water + coolant. So I won’t cast indictments for manually flushing in order to avoid the T fitting route.
 
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2018 Dodge Challenger T/A Plus in Yellow Jacket w/5.7L and A8 automatic
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Performing a drain and fill via the lower radiator hose will yield a decent percentage of actual old coolant removed versus simply draining through the radiator petcock.
 

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You can still use one of those heater hose T inserts, but coolant is circulating through the heater core regardless of HVAC settings, so no need to mess with the heater settings while doing all this.

Also, some folks shy away from that approach since it pretty much guarantees tap water will be left behind inside the coolant system to mix with the incoming fresh coolant/water mix. I’m not one of those worry-warts, but they are out there for sure.

Worrying about the adverse effects from mixing a pint or less of tap water with 15+ qts of coolant mixture is akin to circumcising a mosquito IMHO.

But hey, I’ve seen pictures of some of y’all’s garages on here, and I understand some of y’all’s mental state is such that it cannot even entertain the thought of filthy, dirty tap water mixing with your chase, pristine, virgin distilled water + coolant. So I won’t cast indictments for manually flushing in order to avoid the T fitting route.
Once it is drained can it (OAT) be replaced with the green stuff?

What about the GM orange stuff in my inner cooler? Can that go to the Purple stuff dodge uses in the Hellcat inner cooler? (Whipple)
I do not know why the installer put GM crap in it.
 

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Once it is drained can it (OAT) be replaced with the green stuff?

What about the GM orange stuff in my inner cooler? Can that go to the Purple stuff dodge uses in the Hellcat inner cooler? (Whipple)
I do not know why the installer put GM crap in it.
Don't recommend it - the pH level of the old ethylene glycol (aka: green stuff) isn't good for much of the aluminum components in the LA / LC vehicles.

nowadays you have aluminum heater cores and the steel coolant pipes and all the plastic elbows.

for your intercooler - you could run a variety of coolants in those (I'd check with the maker, just to make sure)
 
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I sure don't. Flushing the green stuff every 2 years? Don't miss that.
neither do I. many owners rarely did that schedule, and it would be a mess
 
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The Bacon Hauler (‘12 Cop Charger)
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Once it is drained can it (OAT) be replaced with the green stuff?

What about the GM orange stuff in my inner cooler? Can that go to the Purple stuff dodge uses in the Hellcat inner cooler? (Whipple)
I do not know why the installer put GM crap in it.
Technically speaking, you could use any of the various engine coolant chemistries (OAT, HOAT, classic green, PHOAT, etc.) once the system has been drained and cleaned of the previous stuff.

Mixing different chemistries is certainly bad, but switching to a different one isn’t necessarily bad (as long as the system is cleaned of old stuff).

GM’s Dexcool (and its generic equivalents) are silicated OATs with 2HEA. Mopar’s purple stuff is not a silicated OAT, and I’m not sure if it uses 2HEA. So there is a difference despite both being OAT.

If you are just going to drain the entire system and refill, I would go with a Dex-clone and be done with it. You can get gallon jugs of it at Walmart for dirt cheap.

But hey, what do I know. My 2012 Charger came with HOAT, and it’s got Dex in it now (has for the last year or so). And my 2014 Charger came with Mopar purple and it’s also got Dex in it now. Between the two of them, I’ve got about 75K miles running the “wrong” coolant, and nothing has blown up so far.

This all assumes the vehicle is past its warranty period obviously. If it were still under warranty, running whatever the OM specifies is the only way to go.
 

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How do you flush these modern radiators?

Back in the day I would install a fitting in the heater hose, attach a hose to it, turn the water on, start the car, turn on the heat and open the drain on the radiator and let the hose run until the water ran clear from the radiator.
the best way to do it - and its a bit labor intensive

drain the radiator and then remove the block drain plugs - the water pump sits up so high in these engines that nearly 1/2 the coolant is still in the block's water jackets.

having done 3 cam swaps prior to #4 (April 2021), this go-around I removed the block drain plugs as I was removing cylinder heads. I wanted everything absolutely dry an dealing with coolant spilling out.
- as a result I filled a 3 gallon bucket within 2" of the top edge. That never happened with simply draining the radiator and then tearing down the front cover off the engine.

I used to get coolant tricking out of the block's passages where the water pump fed - and now realize the block held nearly 1/2 the coolant.

By doing this, you've removed most all of the coolant - you could then fill with plain water, run it and drain everything again and then refill with the fresh 50/50 ratio of coolant & water (distilled)
 
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Technically speaking, you could use any of the various engine coolant chemistries (OAT, HOAT, classic green, PHOAT, etc.) once the system has been drained and cleaned of the previous stuff.
Mixing different chemistries is certainly bad, but switching to a different one isn’t necessarily bad (as long as the system is cleaned of old stuff).
I was always of the understanding that not all gaskets and seals are compatible with all different types of antifreeze.
 

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The Bacon Hauler (‘12 Cop Charger)
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I was always of the understanding that not all gaskets and seals are compatible with all different types of antifreeze.
2HEA was blamed, some say scapegoated, for the infamous gasket problems GM had after introducing Dexcool back in the day, and so it is an ingredient some folks don’t want their coolant to use, just in case.

I’d have to look at the MSDS for Mopar’s OAT coolant to know if it uses it for sure or not, but either way, I’m not sure there is enough evidence it’s harmful to the types of gaskets used in these modern engines anyway…the kind that come into contact with the coolant anyway.

I’m close to 50K miles using the Dexcool in The Bacon Hauler, so if the engine’s gaskets are going to turn to mush from it, surely it will make itself evident pretty soon with a visible or audible leak at the intake or water pump.

I’ll update my replies with the proper mea culpa in the unlikely event that does occur.
 

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I’ll update my replies with the proper mea culpa in the unlikely event that does occur.
An update on that Taurus transmission swap would be much obliged, Sir..........
 

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The Bacon Hauler (‘12 Cop Charger)
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An update on that Taurus transmission swap would be much obliged, Sir..........
That turd will not be getting another transmission. I’m going down tomorrow to clean it out and fill it up with some generic ATF.

If it will run and drive after that, I’ll sell it to the first person that has $500 cash or a bag of wet cat hair to give me in return.

If it does not want act right after that, I’m gonna load it onto a trailer and drive it to the nearest boat ramp I can Google Map on the local lake. Once there, it will be unloaded and left for anyone that wants it…possibly below the water line though, so they’ll need to be scuba diving to find it most likely.🚢🛥🛳
 

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Seems such a waste of transmission fluid........
 
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Seems such a waste of transmission fluid........
Yeah, but at least it will actually get used in the Ford for which it was purchased, as opposed to the parts I’ve purchased in the previous two attempts at working on that Ford.

Both of those parts purchases ended up fertilizing the grassland around the ranch house instead of getting installed as intended.
 
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