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(14,408 posts)
Wed Feb 7, 2024, 08:43 PM Feb 2024

When did the automotive coolant war commence?

My first new car was a 2000 Saturn SW2 (small station wagon), and my second was a 2005 Saturn Relay (minivan).

Green (old Ethylene glycol) and Orange (Dex-Cool) were the options I was aware of.

Today, with three recently acquired used vehicles (2006 Dodge Grand Caravan, 2016 Honda Odyssey, 2017 Honda Accord), now I contend with G05 (HOAT) and Honda Blue (not sure of it's formulation), which are but a few of the options.

Honda Blue in my Hondas is everything I read that one should only use and never, ever anything else.

G05 is what's recommended in my Dodge.

Mixing coolants varies online from a mortal sin punishable by death because your coolant will turn into gelatin to meh.

I had Jiffy Lube do a coolant exchange in the Dodge, but I cannot find what formulation they use. I'll stop by and ask, but I question whether they'll really know. There are so many formulations it seems inconceivable that they stock everything, so I suspect they use some sort of "universal" coolant that "mixes with everything." It looked like G05, so when the water pump started leaking [a LOT], that's what I topped off with. Keeping an eye on it to ensure it doesn't turn to gelatin.

The warnings are sufficiently strong regarding Honda Blue that I keep an eye on the coolant in both Hondas. I removed and cleaned out the overflow tanks, which was very easy in Hondas. [Less so in the Dodge.] I plan to get the coolant exchanged by the local Honda dealer since I presume the odds are best that they'll really, really use Honda Blue.

Coolant should not be this hard.

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(26,115 posts)
1. Had a chat with our independent guy about this a while back.
Wed Feb 7, 2024, 08:49 PM
Feb 2024

He's in a shop that has probably 200 years' worth of expertise, and they've been working on our cars for nearly 20 years.

Anyway, he said that it's pretty important to stick to what's recommended because they all work a bit differently. Some are interchangeable, especially as new standards are released. I think you're right that the dealer would be using exactly what's recommended, but I'm sure the service manager would be more than happy to confirm.


(14,408 posts)
2. It's my understanding that one cannot discern between coolants by color
Wed Feb 7, 2024, 10:05 PM
Feb 2024

The color is just dye, there's no industry standard, and different manufacturers use different colors for different formulations. Even if it's the same formulation and the same color, different manufacturers' products could be incompatible.

Apparently no way to test, easily or inexpensively, what coolant is in the vehicle.

If you buy a used vehicle, it's safe to get the coolant exchanged professionally so that you know.


(26,115 posts)
3. That's my understanding as well.
Wed Feb 7, 2024, 10:27 PM
Feb 2024

And agree that coolant is one of the things that should be changed on a newly-acquired used car.


(1,397 posts)
4. My understanding is...
Thu Feb 8, 2024, 09:48 AM
Feb 2024

That the old standby was fine for cast iron, new formulations were needed with different aluminum engine castings, aluminum radiators, gaskets & plastic parts. I'll dig up my textbook on thermal expansion & interface sealing, on second thought, just use the manufacturer's recommended formula. Have fun....

Old Crank

(3,993 posts)
5. Certainly not like the good old days
Fri Feb 9, 2024, 04:48 PM
Feb 2024

Antifreeze was green and you topped off with water. When you drained it out is was usually brown or red from internal rusting.

I think the formulations have improved but you need a chart for youir cars to make sure you have the right one for each vehicle. Not to mention a whole shelpf in the garage for coolants and oils....


(4,953 posts)
6. If you want to be 100% sure, go to the dealership parts department(s) for your vehicles
Mon Feb 12, 2024, 10:02 AM
Feb 2024

Give them the vehicle information, and ask them what is now the recommended coolant for each.

Car manufacturers routinely issue what are known as Technical Service Bulletins (TSBs) to their service and parts departments. On my vehicles, which originally came with the orange coolant, Ford issued a TSB changing the coolant over to P-OAT. When I had to replace the water pump and hoses on my truck last year, I flushed the engine and put in the new P-OAT coolant. I'm going to make another post about these new coolants, and the importance of only using distilled water.


(4,953 posts)
7. IMPORTANT Notes on OAT-type Coolants (Former Technician here)
Mon Feb 12, 2024, 10:15 AM
Feb 2024

When adding engine coolants to a vehicle, its important to know exactly what coolant is in the engine.

There are several different types:

-Inorganic Additive Technology (IAT)
-Organic Acid Technology (OAT)
-Hybrid Organic Acid Technology (HOAT)
-Phosphate-Free HOAT
-Phosphated HOAT
-Silicated HOAT

If you're dealing with a coolant leak and do not know the type of coolant is in a vehicle's engine, the safest play is to add Distilled water. DO NOT add tap water or filtered well water, as chemicals and minerals in tap and well water (especially municipal system supplied water) may react poorly with whatever coolant remains in the engine.

If you're changing out coolant or adding coolant to an engine with no leaks and you've purchased a gallon of undiluted OAT coolant, cut this undiluted coolant 50/50 with Distilled water BEFORE adding it to the cooling system.



(14,408 posts)
8. The Caravan leaks, but it's a Dodge so par for the course
Mon Feb 12, 2024, 12:42 PM
Feb 2024

The coolant leak is coming from the water pump, I'm reasonably certain.

Oil leak is from the front valve cover and oil pan.

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