Heat transfer - water vs. 50/50 water/antifreeze

I’ll add this comment: When I was young and worked in a garage, water was drained and replaced with a mixture of “permanent” (ethylene glycol) antifreeze for the winter. The mix varied according to how low you wanted the freeze protection to be (I did some cars down to an 80/20 antifreeze to water). In the spring, the mixture was drained and replaced with water and a can of anti-rust/water pump lubricant (made by DuPont as I recall). Most of the then newer cars used a 180 opening thermostat, for the older cars (mostly 1930 - 1940 cars), you pulled the 180 thermostat and put in a 160 open one (or none at all, the owner preferring to put a piece of cardboard in front of the radiator) and used a mixture of water and alcohol. Strange as it may seem, there were not many boil-overs in the summer. OldMotorist

I suspect most of them don’t run thermostats at all since they are just going to warm up and stay hot all day. Some of the races run triple digit speeds and in triple digit temperatures.

I was just making the point that with a vaguely functional cooling system, straight water will provide adequate cooling and won’t boil over, even in ancient cars that are racing at speeds they were never meant to.

Point taken.

Water is the better heat transfer medium, as others have pointed out. I’m willing to bet that the cars in that race not only don’t run T-stats, they probably don’t run pressurized systems either. They probably just circulate the water continuously straight through the engine and radiator without a pressure cap on the radiator and run the engines relatively cool. Remember that a T-stat’s function is not to help the engine cool down, rather it’s to let the engine warm up.

If some one of you is familiar with this race and I’m wrong, please don’t hesitate to correct me. I’m speculating here.

Thermostats regulate the temperature. If the temperature is allowed to run cold (relatively speaking) fuel will condense on the cylinder walls and wash down or coke up. The dew point of gasoline at 150 psi is above 100* F I believe. Also, rings and pistons take a beating when the temperature isn’t somewhat constant. But I don’t deal with racing engines of any kind so I’m just speculating.

Wetter is better! What is wetter than water?

Salt water, for one thing. If the glycol reduces the surface tension of the water, it will wet the surface better and wick heat away more efficiently. I think that’s chemistry, BTW.

“Does anyone here follow the 24 hours of Lemons or Chumpcar series? These are endurance races for cars that cost less than $500 (other than the cost of safety equipment) where basically POS beaters get run as fast as possible around a racetrack for hours upon hours.”

I doubt if they care about that on these cars. I myself have run an old beater 4-banger engine with a T-stat stuck open for about a year with no problems except frozen buns. The engine generated enough heat to run fine, and the mileage wasn’t even that badly affected, the heater just didn’t work. My guess is that they just run these in the race with a wide open cooling system. With antifreeze prohibited, my guess is that their main concern is preventing overheating.

Again, I’m, just guessing. I have no direct knowledge of how they set these $500 beaters up.

I’m glad for you the mileage wasn’t badly affected because gas explodes much more efficiently at 192 degrees than at lower temperature and the pistons and rings are engineered to fit together at 192. Also, emissions are higher at less than operating temperature.


Back in these days, DuPont sold two types of antifreeze: ethylene glycol which carried the Zerex label and a straight alcohol called Zerone. The Zerone had a lower boiling point and often a 160 degree thermostat was used. In the summer, the mixture was replaced with water and a rust inhibitor. I don’t think the cooling system was pressurized back then either.

Water is most efficient, hands down. Coolant is an engineered material designed to prevent freezing in your engine but it doesn’t transfer heat as well. Modern coolants also prevent corrosion, especially with dissimilar metals such as those found in older cooling systems (but only if you don’t allow them to degrade). Never use higher than a 50/50 mix of coolant. I don’t try to guess any more, I use the fifty-fifty mix they sell now, even though I know I’m getting screwed.

Your cooling system is pressurized to increase the capability of the coolant to resist boiling. That works with water as well as coolant. Ultimately, the air going through the radiator is what is cooling your engine, but liquid coolant is a more effective way of getting all the remote points of your engine cooled to a safe temperature. One point to remember: You want the engine to run as hot as it safely can, since the difference in temperature between the cooling jacket is what extracts heat. If the cylinder walls get too cool, you lose a lot of the thermal energy in the cylinders. So I’m not recommending that you use water as your coolant, because the engine was designed to use anti-freeze. But when you’re not sure, water is safer.

If this is an engineering question, you will find the answer in any automotive engineering text, or in a mechanical engineering text. You don’t even have to consult a car application. Turbines, reactors, boilers, etc., all use water, not anti-freeze type mixtures, because water conducts heat better than any other fluid except liquifiied gases.

Let me add this to my previous post: The science behind the engineering will take you to “specific heat” of the substance (not to be confused with specific gravity, which is a factor in specific heat). The calculation is based on the amount of energy a given mass can absorb before its temperature is raised one degree Rankin. I believe it is BTU per pound in liquids and solids, BTU per mole in gases. The point is that water is the standard at 1.007, although ammonia (which has a very similar molecular structure) can be very slightly higher. Higher weight materials, such as oil and Ethylene Glycol, can HOLD more heat, but we want the material that can absorb fast and then release fast again to another surface like the radiator. That’s water, because it is wetter, allowing it greater surface contact than other materials. It is possible to make water even wetter by adding an emulsifier (reduces surface tension of water molecules) such as glycerine, which is the basis for many soaps.

Thank you for this very complete data. You have given readers a lot of information they probably didn’t have before.

The plain and simple answer to your question is:

100% water as engine coolant, will transfer MORE heat from the engine to the radiator than any “mix” of ethylene glycol and water.

The majority of answerers here are not understanding this, and answer improperly.

Without a complicated, scientific sounding answer, just understand that water holds and transfers MORE heat than any water - ethylene glycol mix. Pure ethylene glycol is even worse!

False info. Sorry.

Wrong. Sorry.

Besides reopening a 10-year-old thread, you’ll need to actually provide some information. I’m correct that 50/50 can operate at higher temp, increasing the temp difference from radiator to air. What’s your point?

Sorry, but it DOES have a mesningful value, along with the several benefits of ethylene glycol.

Plain water holds/transfers MORE heat than a mix of ethylene glycol and water. Pure ethylene glycol is the worse concentration for heat transfer. Water is the best. A mixture is somewhere in between.

@americanenglish101_145976 2 of the people you are replying to have not been on the site for sometime . Frankly I don’t see the purpose of reviving this 8 year old thread because a person would have to insane to use plain water in a vehicle anyway.

You are correct and you are wrong :wink:
Water IS the best at transferring heat. However, plain water has an issue with localized boiling due to surface tension. It needs a surfactant to counteract that issue. Which is why you see racers using products like Water Wetter to reduce surface tension and prevent localized boiling. Those engines get torn down and rebuilt regularly so the added benefits of corrosion protection in commercial coolants is not needed.

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This thread is old, but since I cam across it in my search today I wanted to reply. Straight water is better at removing heat in a radiator (assuming the same temperature differences in the two medium transferring heat) for two reasons: 1) Water has a better specific heat capacity than ethylene gylcol, 2) water has a lower viscosity (i.e. it mixes better in the radiator and engine). I came across a graph that was produced by Prestone that showed that 50% water/antifreeze mix has about 50% the capability of removing heat as pure water (I think this is the same value Water Wetter states) . Thus, lowering the antifreeze concentration (within the winter time limits of your geographical area) should help keep coolant temperatures lower. Below some minimum antifreeze concentration (I like to say 25%) requires the use of supplemental corrosion additives (Bars Leaks makes a water pump lube/corrosion inhibitor). Antifreeze does provide some boilover protection, however it is less than 10F as most of the elevated boiling point is provided by the pressurization of the system.

Using straight antifreeze in your vehicle can cause elevated coolant temperatures without boiling occuring. You may very well be able to transfer more heat due to the elevated coolant temperature, but be aware of the possible detrimental effects regarding the engine oil thinning. An article I read at noria.com stated that each 10C increase in oil temperature makes it act as if it was one “weight” thinner (i.e. a 30 weight oil would act like a 20 weight oil). If your vehicle tends to overheat, then you might want to consider using a thicker oil.

I do want to correct one statement made in one of the threads regarding the use of Water Wetter (someone else may have corrected the statement; I didn’t read all of the posts). Water Wetter acts as a surfactant and reduces the surface tensioni of water making it MORE likely to turn into steam at nucleation sites within the engine (i.e. typically within the coolant passages in the heads since that’s the hottest area). Nucleate boiling (i.e. creation of small steam bubbles that then collapse within the bulk stream of the coolant passage) increases heat transfer and is actually designed into pressurized water reactors (i.e. nuclear reactors) and many other systems (probably automotive as well). Water Wetter’s reduction in surface tension increases localized boiling which reduces cylinder head temperatures (which is what Water Wetter advertises; they don’t advertise lowering the bulk water temperature).

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