Question: I ran across a great matrix chart of the various coolants available. Six coolants have checks in the HOAT column, and five of these are listed as meeting DaimlerChrysler OEM specifications.
If the chart is accurate, I’m curious why the Mopar HOAT coolant has a check in the w/out Phosphate column, but the Zerex G-05 does not. I had assumed these two coolants were exactly the same, save the orange vs. yellow dye.
http://www.eetcorp.com/antifreeze/Coolants_matrix.pdf

It is a good reference chart and I am saving it for closer study. Dont know about the phosphate question. These formulations can be complicated to design, and still have everything work as it should. Some work I did about 10 years ago would have lead me to believe that a little phosphate was extremely desirable, especially where iron or steel is involved.
A type of corrosion is found where steel is exposed to water based systems (although they are oxygen free and elevated pH) that is easily stopped by a very small percentage of phosphate.
The reason why phosphate is not used in some of these systems is not intuitively obvious.
The simple answer is obvious, buy ethylene glycol (or propylene glycol) and DI water “straight up” and add your own additive package as needed. Of course although a 55 galon drum of glycol is available, the additive packs aren’t.
Is there ONE coolant good for a Series 60 Detroit Diesel, a V-1710 Allison, a Honda Civic, a Ford Focus and a Isuzu powered Thermo-King reefer unit?
I’ve been using Dex-cool ever since stores started carrying Havoline Extended Life and have never had problems. This is with a VW, Toyotas (incl. a Nova), a Ford (Mazda engine), and a Honda. What did the manufacturers of your cars do wrong?
No, other than the possibility to precipitate magnesium and calcium as phosphate salts, I know of no other reason. Maybe I will research it when I get a few minutes. Perhaps there was something I missed.
We developed some organic phosphates which worked well, and did not seem to have the precipitation problems of the inorganics. These are still used in large quantities in some industries.
I use whatever the manufacturer recommends, but I flush and change out the coolant every couple of years.
As I mentioned before, there is no 100% perfect technology for mixed metallurgy found in todays systems.
Keeping the air out, which the surge tank or overflow tank helped accomplish, did a lot of good when they started to be used years ago.
The biggest problem I saw was a proper inhibitor for aluminum. Silicates weren’t so very great, and they caused precipitation and blockage of radiators.
I havent worked on this in 4-5 years now, and hope that significant improvements have been made.

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