Pure Coolant

I’ve heard people say they use pure coolant and no water in their cooling system. Doesn’t this harm the water pump?

What else can it harm?

Increasing the concentration of antifreeze above 60% actually hurts the engine?s freezing and overheating protection. More is not always better!

I believe it is done in climates where extra protection is needed because of extreme temperatures. Unless that applies to you, I wouldn’t do it. I doubt would do any harm, but I suppose it might if the product is concentrated, and depends on the added water to work properly.

“Coolant” is actually a misnomer, because “coolant” doesn’t “cool” as well as water. That’s why you add water. What you’re talking about is “antifreeze”, which is a mixture of non-freezing chemicals and anti-corrosives to protect the metals in your engine. Anyone who runs pure “antifreeze” is risking overheating their engine. If pure antifreeze worked better than a mixture of antifreeze and water, dontcha think that’s what the car makers (and antifreeze makers) would recommend?

Some antifreeze comes pre-mixed, so you just pour it straight in instead of mixing it with water first. Some people get confused about that, and think they’re using straight coolant.

Two Different Coolant / Antifreeze Choices Are Available; Straight, Undiluted Stuff (Not Ready To Use) And The Stuff That Is 50 / 50 Diluted With Distilled Water (Ready To Use).

Is this possibly causing the confusion with what you are hearing ?

Straight, undiluted coolant freezes at a higher temperature than properly diluted coolant and causes an engine to run hotter.


Actually a 60/40 AF to H2O mix gives protection to -60 degrees. After that you gradually start losing freeze protection. I can’t think of many places even Alaska that gets much colder than that!

Since We’re On This Topic . . .

If any of you store coolant in an unheated garage or if you’re handling coolant (changing it, adding it, etcetera) in cold weather, be careful !

Several years ago I spilled a little coolant (ambient temp below 10F) on my hand and it instantly caused frostbite (frozen flesh - turned white).

Also, similar deal . . . those walking dogs in the winter, be alert to the fact that salted, melting snow / slush on a below-freezing day can painfully freeze the animals paws should it walk in it.

Cold liquids cool flesh much faster than cold air. How long can you survive in 40F air ? How about 40F water ?



I had to look it up, but pure anti freeze (ethy. glyc.) freezes at -8F.

In the really cold places, they generally keep a block heater going when the engine isn’t. In any event, pure anti-freeze will freeze sooner than a water/anti-freeze mix, if I remember the charts that I have seen correctly.

Along those lines everyone should also be aware that pets consider coolant to be a tastty treat, but it’s actually toxic. Any spills should be well cleaned up and any residue washed away.

The temperatures to which a coolant mix will protect are in a chart on the back of the bottle. Pure coolant will not protect to as low a temperature as a proper mix.

But pure coolant will not harm the water pump. Unless, of course, it freezes…

Coolant in water has a higher boiling point than water alone. Therefore it is both coolant and antifreeze.

Yes, but my point was that pure antifreeze has a lower thermal conductivity than water and therefore is not as effective in conducting heat away from the engine as a water/antifreeze mix is. It’s not just a matter of boiling points, but also thermal conductivity.

As I recall, the recommended water/coolant mix is also better at conducting heat than either in pure form.

Not rocket science.

Mix antifreeze with water at 50/50 mix ratio. Provides the best antifreeze/boiling point protection all year long.


It depends. Unless they’ve changed their policy Subaru recommended using pure anti-freeze as it was less corrosive to aluminum.

On a side note, the leaking and rotted out timing covers I’ve seen on Ford small blocks had one thing in common (at least near as I could tell); aged or heavily diluted anti-freeze.

I’ve run pure anti-freeze quite a few times over the years and have never had a problem because of it. Just my 2 cents anyway.

Most people still think that. But, it has been quite a few years now that anti-freeze has been reformulated, and will provide better antifreeze and boiling points at a greater percentage than 50/50. Go to a parts place, and look at the charts on their good anti-freeze containers. I retired in 1997, and it was several years before that.

However, the 50/50 is adequate for most normal circumstances.

Did they also tell you to use an antifreeze/water mix if it dropped below about 0F outside? Just wondering because that sounds strange since pure antifreeze doesn’t work as well as a “coolant” due to lower heat transfer abilities.