pH of coolant


Donating Member
Has anyone tested the pH of their coolant? I am a chemist and thought I would check mine to make sure it was not acidic. Well, I was shocked to find the pH around 10, which is basic. I thought maybe it came from using a flushing solutions when I changed from Evans back to ethylene glycol. However, the Prestone was also around pH 10. Since I use distilled/RO water for dilution, there is no buffering capacity and of course the entire solution is at pH 10 also. This seems way to high to me. Anyone have some ideas on this?

Ok once again in english, cause i have no idea what you are talking about lolol J/k at what point does it begin to affect the cooling ability?

I have never given it much thought why you would want a solution to be either a base or an acid. The only thing that I can think of would be that maybe a base would be "easier" on the internals (metal and hoses) than an acid would be.

Another thought comes to mind would be the environmental impact of a base vs. acid.

If you get a definitive answer, let us know.
Well, you definitely do not want it to be acidic. What can happen, at least in autos, when the coolant is "never" changed, it can in time become acidic. That is when it starts to eat headgaskets and other internals, which is bad. Just for the heck of it, I decided to check the pH of the Busa's coolant, VERY BASIC. Basic can also be corrosive, but generally not like an acid. I am very curious about this. I will write an email to Prestone and see what they say.

When they say high pH (lots of OH- in it) chemicals are corrosive they generally mean to you, not the vessel (the slimy feel of oven cleaner is due to your skin dissolving, but your oven will be none the worse).

High pH is generally good for metals (steam boilers rely on this not to fail). Ironically, some acids (low pH, Sulphuric) can be stored in steel tanks but only if it is like 99% strong. Where as few % solution will eat neatly through it and turn Aluminum to a white power in no time.

If you have unlackered Aluminum rims you may notice a white powder where the drops of rain water have evaporated, that's acid rain for you (or salt), leave it standing long enough and it will pit.

 Anyway: High pH is good but  will produce sludge (esp if your water is hard), that's why you should use "distilled" or Di water. If you got this far without :drink: .....

The preceding text may or may not have been purely fictional and is in no way based on persons, living or dead.

:type: - Amen.
Absolutely correct. I am curious what they add to the ethylene glycol to bring the pH up to 10... that was surprising to me. I found a web site that stated that coolants should be between 9 and 10.5 for optimal effectiveness. I guess I am good to go!