How much anti-freeze is to much

I had to pull the radiator 3 times and ended up with a high a freeze point somewhere above -60
It pegs my gage. Is that going to hurt anything?

You can go up to 70%, after that the freeze point starts to rise back up. The lowest freeze point is around 66% and the highest boiling point is around 70%.

If you use propylene glycol (Safer) instead of ethylene glycol, you can go all the way to 100%.

The richer mixtures offer more corrosion protection, I go with a 2:1 ratio and it pegs the gauge also. It has never caused any problems for me.

The problem with pure antifreeze is that it has a poor specific heat capacity. As the mixture ratio goes above 50/50, the coolant will run hotter to get the heat out of the engine. At some mixture ratio, the remaining water in the mixture will boil causing excessive hot spots in the engine (think exhaust passages, spark plug seats, and exhaust valve seats) Eventually, the head will overheat due to collected steam bubble and the head will probably warp. This would happen when you are pushing the engine hard and where you could not pull over easily.

50/50 is the highest mixture ratio I have seen recommended. If I don’t pour the old coolant back in the radiator after a change, I will premix 50/50 with distilled water and use that as replacement. In fact, I carry a gallon of 50/50 premixed in the car for emergency replacement.

Hope this helps.

I ran 2:1 in my Saturn through death valley at 121F, with the AC on and going up that grade into California. The water in the mixture will not boil and the increase in the ability of antifreeze to transfer heat off sets the heat capacity difference.

One brand I seen has 70/30 right on the container

The best COOLANT is pure water if heat transfer is the only consideration…

The freeze point of pure ethylene glycol is 9 degrees F, however, it doesn’t expand when it freezes so it won’t crack your engine block, it will, however lock up the water pump and prevent circulation through the radiator.
There are only a few substances that expand upon freezing, bismuth, antimony, gallium, and something else that I can’t think of right now…oh wait!, I remember now!,…water!

Where do you live? If the goal is to keep things from freezing in ridiculously cold weather then you should be ok. But if you have warm weather in the summers you’re going to want to get that mixture down to about 50%. Antifreeze does a poorer job of transferring heat than water, so a system of pure antifreeze will run hotter in the summer than a system with 50/50. Pure water will run even cooler. Of course water offers no anti-corrosion protection.

I have to disagree with you on pure water’s ability to transfer heat. I have personal experience from back in the day when antifreeze wasn’t so common. I had several cars that would overheat on pure water but did not with a mix of antifreeze in them. Because I lived in So. CA at the time, I used to run only 25% antifreeze.

Water may have a higher thermal mass, that is the amount of heat, measured in BTU’s needed to be exchanged to get a volume of water to change its temperature, but that does not translate to heat transfer. Water is bi-polar, that is each water molecule has a magnetic field and because of this, it has more surface tension. That inhibits heat transfer to other surfaces through conduction. Antifreeze breaks the surface tension.

Having a low thermal mass means the coolant gets hot quicker in the engine and cools off quicker in the radiator. You just have to flow the coolant faster through the engine.
A benefit of the low thermal mass is that the engine warms up faster. It took a long time to get the four gallons of water in an old cast iron six up to operating temperature in the good old days.

I’m in Fairbanks Alaska
It sounds like if I want freeze protection & max heat

I’m also in the Fairbanks area. The indy repair shop I use recommends freeze protection down to 60 below. With our winters, anything less in interior Alaska is taking a needless risk.

A word of caution here. Those coolant testers do not actually measure the freeze point of the coolant, it only measures the specific gravity of the coolant. If you go over the 70% maximum with ethylene glycol, the tester will still peg out, but your freeze protection will actually be less (freeze point rises).

I would suggest that you pull a sample and measure out a specific quantity, say one cup. Then add pure water, about a table spoon at a time and keep measuring the coolant with each addition. When the mixture gets to 50/50, then you should be able to calculate whet the starting concentration was. If it was over 70%, then I would drain a little out of the system and add just enough water to bring the mixture down to the 66 to 70% range.

@allen51 I agree; do what the locals do and recommend. That’s better advice than some of the lower 48 posters can give.

While you guys are talking about coolant and water, I have an interesting story. Friend had a Jeep that was overheating. We were trying to figure it out. The fan was fine, no leaks, radiator looked okay, he changed thermostat and this didn’t fix the problem.
Finally, one day we decided to take his water pump out. There was nothing behind the pump assembly, no blades. Turns out he had been putting only water in the cooling system (hot climate), and this rusted out the water pump, but it wasn’t leaking.