Antifreeze color. Important?

[Iowaboy]

Which is the correct antifreeze to use in my 50 Dodge with the 218 flathead. I had to drain it to replace the upper radiator hose, and decided to replace all of the fluid as it had not been done for at least 39 years it was in storage. 

The used fluid was kinda green. The antifreeze I got at Walmart is kinda yellow.. I’ve heard that some is pinkish?

is there a wrong color to use? It tested to 25 below zero even though it was very old. ?

 

[Dodgeb4ya]

Inorganic Acid Technology or IAT: This is the common green stuff original equipment manufacturers have used for over 70 years. Ethylene glycol is its base chemical and there are silicate and phosphate additives that make it compatible with copper, brass, cast iron and aluminum cooling system components. Manufacturers recommended that you change the green IAT antifreeze every 36,000 miles or three years.

As above use the standard old green Antifreeze coolant.... nothing fancy or you might get into trouble!

[John-T-53]

This was posted over on the "For C Bodies Only" Forum last year. I learned a lot about coolant starting here:

 

https://www.forcbodiesonly.com/mopar-forum/threads/ethylene-glycol-or-the-new-permanent-anitfreezes-for-our-original-mopars.38985/page-2#post-587387

 

IAT (Inorganic Acid Technology): This is the green stuff that we are used to running in our old Mopars. It's actually getting difficult to find now.

OAT (Organic Acid Technology): Dexcool is an example of this. DO NOT USE in cooling systems which contain copper or brass components. The additives package does not contain corrosion inhibitors which protect copper/brass. DO NOT MIX with IAT or it will form sludge in the cooling system.

HOAT (Hybrid Organic Acid Technology): Can mix with IAT or OAT without causing sludging. HOWEVER, it may not provide adequate corrosion protection if mixed. A half-charge of one type of corrosion inhibitor and a half-charge of another type probably will not equal the protection of a full charge of either.

Modern Prestone Universal "mixes with any color antifreeze" is a HOAT. If you're going to use it, I recommend you flush and fill ONLY with Prestone. However, my recommendation is Zerex GO-5. Available as pre-mixed from Walmart and as a concentrate from real auto parts stores.

GO-5 is a HOAT and is the same stuff that is factory fill in many modern Mopars, even though it's not the same colour. (GO-5 is a pale yellow that is unfortunately hard to see through the side of the reservoir.) It offers corrosion protection for copper/brass. I converted my '94 Cummins to this. When the coolant in my Chryslers is due to be changed, I will probably convert them over to it also.

EDIT: A tech note I found on G-05. Couldn't find anything comparable for Prestone.
http://www.consulab.com/files/zerexg05TechBulletin.pdf

Edited May 6, 2019 by John-T-53