Ok, I've compiled a short list of some myths on antifreeze and some questions and such that I found throughout this forum and some websites.

M. Pure antifreeze freezes at higher temperatures than 70% - 50% mixtures.

F. Depending on your coolant, whether it's propylene glycol or ethylene glycol based, the pure antifreeze will freeze at -74 to -80 and 14-20 degrees F respectively. This is roughly the same as a 70% solution with water (at least with propylene).

M. Pure (distilled deionized) water will leach metals from the coolant system as opposed to regular tap water

F. All water will leach ions from a coolant system that contains an anode metal and cathode. Contaminated water will actually do this sooner than pure water, because pure water needs time to erode and gather ions to lose it's resistive properties against electricity. Yes, if you had pure water, it would not conduct electricity. This property immediately falls off as the water becomes contiminated, this newfound conductivity of ions allows it to corrode your coolant system. Water wetter is not an antifreeze but it does alter the characteristics of water such that it's ionization is greately decreased, allowing for lower surface tension (it's better cooling properties) and a significantly higher electrical resistance. On the order of multiple megaohms. Antifreeze has the same deionizing effect. Note: contamination occurs in pure water by a few different means, errosion (non chemical reaction) and anodes / cathode reaction. This is why running pure water alone isn't good, most people have iron or aluminum parts and copper parts. And even if you still disagree that pure water coolant doesn't leach faster than tap, you shouldn't be running straight water anyway, it causes a high pressure issue for your coolant system and hot spots in the engine.

M. Mixing dexcool and green antifreeze will cause copper corrosion and damage the car.

F. Colors dont dictate the makeup of the antifreeze. Dexcool's main incompatibility and source for numerous complaints is it's anti-corrosive chemicals. So while the saying is a myth, it's only one because dye doesn't dictate chemical makeup. Dont mix dexcool with anything that's not dexcool approved with the gm logo and everything. I've personally seen what happens when you aren't strictly following the rules with dexcool in a 2001 grand am GT. Unless you like sludge in your coolant system dont do it.

M. Pure antifreeze will overheat the car and destroy it.

F. This is the hardest topic. Gylcol has a higher viscosity than water, running it pure can put a higher strain on the water pump and can cause weaker ones to fail or failure to occur at an accelerated rate. propylene glycol, more than ethylene, has a higher resistance to thermal transfer. This makes it better for colder and hotter applications, where the engine can actually function in those ranges. This can be confusing because it's a given that water alone, will conduct heat better than any antifreeze solution, which is why if you're operating in the safe temp zone of water, it's ideal.
The problem occurs when you near the edges, frozen water doesn't help you any when your block is cracked or water isn't able to leave the block when the radiator freezes. Also, on the opposite end of the spectrum, steam doesn't cool the engine very well. The thing is, even if your mostly water coolant shows an acceptable temperature, this is an aggregate, local temperatures inside the block where the heat is actually being transferred often exceed the boiling temp, and can cause pockets of steam to occur that lead to hot spots.
This is where antifreeze comes in, antifreeze makes water less efficient, and by doing that, it allows to to not pass those barriers that make it completely useless, barriers that we often see every day. Racing engines see extreme high temp, they usually use completely glycol or other more exotic chemicals to cool the engine, since anything water based will simply boil over and produce not only useless steam, but high pressure caused by the steam.
So to respond now to the actual myth, will pure propylene glycol antifreeze overheat your car, unless the pump fails, no. It will increase the temperature a bit, and you may have to compensate for this by getting a lower thermostat. It will reduce the chances of blowing the radiator a hole since the vapor pressure will be significantly lower in a pure glycol system. Despite raising the temperature a bit, you will lower the temperature of the hot spots that used to occur where water was being vaporized, since propylene glycol requires a temp over 150F higher than water to boil. Solutions of 70% are some 50-60F higher than water.
Now I know some people who race will say they use straight water because water cools better. Water does cool better, too good in fact for the temps you see even in a quarter mile race. It will vaporize on contact with hot spots in the engine and that pocket will remain a gas, getting much hotter than it should. Vaporization itself is an excellent way to cool, but once it's vaporized, that vapor has to escape into the atmosphere to remove the heat energy from the coolant, this doesn't easily happen in our coolant system. So you can still see an overall lower coolant temp, without even knowing that there are isolated parts of the engine at a much higher temp. This possibility is avoided with something that doesn't boil at as low of a temperature as water.



The last one was pretty large and by now you can probably guess which way i'm biased when it comes to antifreeze mixtures and such. I run straight extended life prestone. Is there a noticable difference in how fast it heats up and how hot it gets, yes. Is it dangerous, no. Stock coolant system is more than capable of handling cooling down the antifreeze. I found it to be a nice way to counter the effect of running cooler than I should be with TBI while maintaining a more uniform temperature. There is also the effect of having a coolant that is pretty much completely non-conductive so leaching of metals is almost absolutely eliminated and vapor loss is nearly gone too. I'm not saying running a solution with water wouldn't give you a more ideal situation either. I was just a little frustrated researching other people's experience with antifreezes and seeing the same back and forth arguments.

If anyone has anything to add to the myths of antifreeze go for it. These were all the ones that i was concerned with. It's not a strictly informational thread, since i've added some additional biasness towards a higher concentration of antifreeze to water. Though, I may later go ahead and pull a bunch of published scientific (peer reviewed) studies to back up the "factness" of the facts described aboved in order to perhaps make a sticky of myths. It'd be really cool to have such a sticky for each forum section since so many people come in with similar notions of what's going on when it's really not, or it's not as significant as thought. I've done that numerous times.

 

What about information regarding the latent heat capacities of the various types of coolant, but in full concentration and dilute forms?

 

you can get some chemical info regarding the base components of the antifreeze and info regarding aqueous solutions containing them. but specific antifreezes have different additive.

some solution info can be found here http://www.lyondell.com/html/product...dustrial.shtml

the pure info can be found here
http://www.chemicalland21.com/arokor.../menupetro.htm
http://www.jcna.com/library/tech/tech0011.html


the last link is quite useful. It confirms just about everything i mentioned above. In a much more elegant and scientific way.

edit: Except that i never mentioned that propylene glycol is flammable. Whether or not antifreezes that contain this chemical as it's base are flammable is not known. There are many additives in antifreezes ...an inquiry into each brand would have to be made, ro someone really keen on testing it for himself. The lack of stories of people putting too much antifreeze in and blowing up tells me that it's likely not in a readily inflammable state in antifreeze.

 

a lil tidbit about dexcool I learned from my (GM master tech with 18 yrs under his belt) ASE teacher

Dexcool isnt safe to use in cars that have/may have leaks of any sort. Any (including tiny pinhole) leaks in a system with dexcool in it will eventually block up the cooling system. When it mixes with air the molecules get much larger (think a warm coolant slushie) in turn causing blockage. A system that isnt air-free is the one that will have a massive amount of issues with it. This is where that whole dexcool issue came up a few yrs back.

 

well then that's gonna be a problem with dexcool.. since no coolant system in any car i've ever seen is a closed system. They all are open to the atmoshere to relieve pressure buildup and to allow for expansion (move into the resevoir tank which is open to the atmoshere) ... so if dexcool is damaged by exposure to air, it would have no place in an automobile coolant system.

 

Anyone old enough to remember the methanol in gallon cans that had to be poured into the cooling system about 3-4 times per winter? If you think some glycols are flammable....