coolant for high temp weather?

[brinu]

I am confused - why a higher concentration of coolant (70/30 or straight 100% coolant) is not recommended for high temperature weather? Can someone explain why a higher concentration of coolant (70/30 or straight 100% coolant)isnt recommended for high temperature weather but at the same time they say that a higher coolant concentration will further increase the boiling point temperature?isnt it better to have a higher boiling?

 

[SC Maintenance]

Because ethelyene glycol does not transfer heat as well as water. So if you don't need the extreme cold protection then a higher concentration is actually a detriment.

 

[Hohn]

Glycol has a higher boiling point but it has a lower specific heat. So it actually doesn't cool as well as water does.

That why products like "water wetter" exist-- they allow a racer to use pure water in a cooling system while still having some corrosion resistance.

So, the ironic thing is that the more you raise the boiling point of your coolant mix, the hotter the engine will run and the closer it will get to needing that boiling point.

I recommend staying no more than 50/50 unless you have extreme cold conditions that cannot be met with that blend. For max cooling, you'd want the weakest Glycol concentration that still allows sufficient corrosion protection.

 

[PWMDMD]

The specific heat of water is higher than ethylene glycol - you can thank water's unequal distribution of electronegativity/dipole moment and hydrogen bonding. It takes more heat to overcome hydrogen bonding to give the water molecules the ability to wiggle more (specific heat) and more heat is needed to provide sufficient kinetic energy for water molecules to separate from their neighbors and vaporize (heat of vaporization). The hydrogen bonds also provide a network for energy transfer between water molecules which increases water's thermal conductivity. So compared to 100% water, ethylene glycol increases the boiling point but also reduces its cooling efficiency. As the % ethylene glycol increases, eventually, thermal conductivity becomes so inferior to 100% water, that it can cause the engine to overheat.

 

[kschachn]

And you don't need to, nor do you want to increase the boiling point of a properly operating cooling system.

 

[Tman220]

A 50/50 mixture at 15 psi system pressure is good for 265 deg F boiling temp. What makes someone think they'll need a temp higher than that?

 

[Rand]

In a very hot climate or for racing you ideally run 30/70 (70% water)
(or even less antifreeze but with additives added)
50/50 is good for most people/places/cars.

and 70/30 for areas that get really cold (-35f or lower)

100% antifreeze is terrible at everything
it does not really work without some water.
as it freezes at around 9 degrees, and the boiling point is 300f+ but does not transfer heat well.

 

[JavierH19]

A 50/50 mixture at 15 psi system pressure is good for 265 deg F boiling temp. What makes someone think they'll need a temp higher than that?

True the boiling point goes up over pure water that's about 250f at 15psi but the rate of heat transfer is lower and can make peak temps higher even though the boiling point is also higher. It's a balance. I run more coolant than water in my old iron blocks because i want to prevent rust more to keep them going longer so I run about 60-70% concentrate but know the peak temps in the hot area like the headgaskets go up so i run a tad lower thermostat and still change every 4 years by doing a lower hose yank but no true flush.

 

[CleanSump]

Because water transfers the heat. The "coolant" raises the boiling point and lowers the freeze point.

 

[Lubener]

I am confused - why a higher concentration of coolant (70/30 or straight 100% coolant) is not recommended for high temperature weather? Can someone explain why a higher concentration of coolant (70/30 or straight 100% coolant)isnt recommended for high temperature weather but at the same time they say that a higher coolant concentration will further increase the boiling point temperature?isnt it better to have a higher boiling?

You will get the best high temperature protection with a 50/50 mix.

 

[Gyro Gearloose]

To add a bit to the very eloquent explanation of specific heat by PWMDMD, the specific heat of pure water is 1.0, meaning it takes 1.0 BTU of heat to change the temperature of pound of water 1 degree F. The specific heat of 50/50 water/antifreeze is about .85 while the specific heat of pure ethylene glycol at 200F is only 0.66. Compared to 50/50 water mix you would have to circulate about 30% more pure ethylene glycol to carry off the same amount of heat and keep the same coolant exit temperature. Further complicating the use of pure ethylene glycol is its viscosity is about 8 times the viscosity of water at 200F and it thickens more than water as the temperature falls.

 

[AdmiralYoda]

Your car, assuming it is functioning as designed doesn't know or care what "High Temp Weather" is. Is 80F considered high temp? 100F, 120F?

There are plenty of vehicles in the world running around in the 130F desert on 160F asphalt in the blazing sun. Humans will be uncomfortable but your car doesn't know or care. It will operate at its designed operating temperature range.

And if you want to increase the antifreeze ratio just so that you don't "Boil over" at a 270F coolant temperature.... well you have other problems that need attention if that is where your engine wants to live when its hot out.

 

[tcp71]

Dealers here sell a concentration of 55/45 coolant to water. It can get below -34C occasionally, which is where 50/50 starts to freeze (gel).

 

[johnmyster]

Unless you're cooling system is undersized and can't keep up, small changes in specific heat of the coolant (even from pure water to pure coolant) are irrelevant.

If specific heat of the mix is lower, the coolant will have a greater termperature rise going through the block and head(s). The thermostat (positioned at the coolant outlet of the engine) will feel this, and open further. You'll get a greater portion of fluid flow to radiator rather than bypass. So, you'll operate with a greater delta for a given heat load, but the delta mostly lowers inlet temperature (T-cold) with a smaller change to T-hot, depending on the responsiveness of the thermostat.

In the power generation industry we would call this a "constant T-hot program".

Also note, for a 50/50 mix, you only get about 12 F of boiling point elevation due to the ethylene glycol. You get another 45 F of elevation due to pressurization (15 psi.) The coolant concentration is the smaller contributor of the two unless concentration is extremely high. EG, your pressure cap is important.