If you live in a warmer climate, why would you waste money on antifreeze/coolant? At $12-20 per gallon, it can get pretty expensive to fill a cooling system, especially in a larger truck or SUV that could take 5-6 gallons or more!
One of the main reasons to use a proper 50/50 mix of water and antifreeze/coolant is because of the corrosion inhibiter package in coolant. Check out the pics below for a prime example. Top photo is from a 99 Ford Taurus that was overheating, bottom is a stock picture.
Next, we have a bit of a paradox: straight water actually transfers heat from the engine to the radiator more efficiently which is why some drag racers run straight water in their race cars. The problem with this, of course, is that your water pump can end up looking like the pics above.
A proper mix also increases the temperature range of the mixture. Regular water boils at 212°F and freezes at 32°F, but with a 50/50 mix you can increase that range to about -34° to 265°F or more.
Last, but certainly not least, coolant is actually a lubricant. If you’ve ever gotten any on your hands, you know it doesn’t just wipe off and dry like water does. The water pump shaft, like any other spinning component, needs to ride on a bearing to reduce friction, and bearings need lubrication.
There are many more articles around which explain the properties of antifreeze/coolant in more detail like this one from Wikipedia (where would we be without Wiki?), or this one from self-proclaimed “Coolant Experts.”
A good concentrated antifreeze/coolant like this Peak gallon jug is meant to be mixed 50/50 with water (preferably distilled water), while there are many 50/50 premixed options out there if you don’t want to bother mixing your own.
Now, if another “polar vortex” comes strolling through America and decides to punch spring in the throat, you’ll be prepared!
*Discaimer: I received no compensation for the above articles and links, and I am not affiliated with any of the aforementioned companies or websites.