Why 50/50 mix and not pure?

[djmc]

My Volvo 850 needs 50/50. Why?

I recently flushed the system with Zerex G-05 (closest to G-48, origional Volvo coolant) but had to mix it down with distilled water for 50% (according to specs).
I wonder why? Why can you not use 100% pure coolant?

 

[kapps]

"pure coolant" will not cool the engine. Water has a very high thermal condictivity allowing it to shed engine heat rapidly. Coolant has virtually zero thermal conductivity. The car would overheat. Coolant lowers the freezing point and slightly raises the boiling point of the water. It also has lubricating properties that are needed for some water pumps. Race cars run pure water because they are always moving and need maximum cooling capacity. If you want better cooling, run the mix with a slightly higher water content like 60/40 ot 70/30. Just make sure there's enough coolant to stop it from freezing in the winter.

 

[djmc]

This is very interesting, never knew that. Thanks.

Now I live in Houston TX and we have very long hot summers and mild winters, but I never heard of people only using water, no coolant. That has to do with the boiling point of water, I guess.
So for Texas summers a 60% water/40% Coolant will be adviced?

P.S. I do a lot of stop and go traffic, every day.

 

[Vilan]

Pure water would cool the best, but the boiling/freezing points are not where a car needs them to be, plus it can rust out your radiator. Adding coolant lowers the freezing point, raises the boiling point, and gives corrosion protection.

Though I reckon you're not too worried about freezing protection in Texas, this link has a useful diagram showing how 50/50 gives better protection than pure coolant.

http://www.gi.alaska.edu/ScienceForum/ASF6/680.html

 

[mazduh30]

Water molecules are spaced far apart, heat travels through water easily. Antifreeze molecules are close together, heat doesn't travel easily. Too strong, you can boil over. Mix with distilled water since it is Ph neutral till you have -34c (50/50) for average climate. Too much of a good thing sometimes is bad...like too strong coolant mix.

 

[Kestas]

This brings back memories of high school and my classmate "scientist". He ran pure antifreeze in his car. A month later he had to junk it because of a blown head gasket!

 

[Ray H]

Deleted - responded to unintended poster.

 

[Ray H]

Why dilute antifreeze 50/50 with water? To enhance its freeze-up protection! 100% ethylene glycol has a freeze point of about -13º C. (By contrast, distilled water freezes at 0º C. at sea level.) But, when ethylene glycol-based antifreeze concentrate is diluted 50/50 with water, the mix will continue protecting on down to about -35º C.
(~-34º F., mazduh30

) Increasing the concentration of antifreeze to 70% will further decrease the freeze-up temperature to a minimum of -84º F. But, a further increase in the concentration of antifreeze concentrate to above 70%, causes the freeze point of the resulting mixture to rise again (reduced freeze-up protection)

.

 

[NYEngineer]

If you live in a warm climate, you can run straight water with Red Line Water Wetter or a similar additive.

 

[kapps]

Yes but some cars require the lubricating qualities of antifreeze for the pump. I'd keep at least 25% antifreeze in there.