edzolz

Does a 70/30 mix of antifreeze cool any better than 50/50? I am working on a friends car and he wants a 70/30 mix with a bottle of water wetter added. Someone told him that would cool better than 50/50 with the water wetter added. I've always heard 50/50 is the best all around mix.

rocketraider

50/50 is the simplest way to mix it and puts freeze point to about -35 degrees. Can't remember where that mix sets the boiling point but it's 250+.

70/30 won't hurt, but not sure of the benefit you'd see compared to a 50/50 mixture. Good idea to use distilled or deionized water if you can get it.

Nilsson

If using water wetter the ratio is different. Look on the bottle it tells you the correct ratio and it is not 50/50.

MDchanic

Here is what I said on the subject last April:

WOW! People do spread some wild rumors, don't they?

The fact is that water has a higher specific heat (Cp = 1.000) than ethylene glycol [antifreeze] (Cp varies with temperature), which means that a gallon of water will accept more heat before its temperature goes up 1° than a gallon of ethylene glycol will, and will shed more heat before its temperature goes back down. This means that a given amount of water will be able to move more heat from the engine to the air than the same amount of antifreeze.

Water does boil at a lower temperature than ethylene glycol, which is one of the reasons why pure water is seldom used in automotive cooling systems: even if the coolant is not boiling out of the radiator, if the coolant is boiling in the passages right next to the combustion chambers (like when you look into a pot that is just beginning to boil and there are small bubbles forming at the bottom), then the bubbles that are forming are not transferring heat well, and heat is not being drawn away from the heads, resulting in hot spots and warpage.

Water also facilitates corrosion inside the engine, especially between dissimilar metals, such as aluminum and iron.

The additives in antifreeze are designed to work best at a 50:50 ratio with water, so that is the ratio you should use. Using more water will improve heat transfer, but decrease boiling point. Using more anitfreeze will do the opposite.
With modern ethylene glycol antifreeze, you should use distilled water instead of tap water, as tap water has contaminants, especially chlorine (if on a town water system), which combines with the antifreeze to cause corrosion.

Here are two tables showing the changing specific heat and boiling points in water / ethylene glycol solutions
(credit to: engineeringtoolbox.com):


- Eric

oldcutlass

Eric, you also have to consider pressure for where water will boil. I believe those figures are at atmosphere.

MDchanic

Yes, absolutely, the boiling points are at atmospheric pressure at sea level, but the increases at 15psi (1 atmosphere for you Europeans) can be calculated and are proportional to the sea-level numbers.

With a mix of 70% antifreeze / 30% water, at atmospheric pressure the boiling point will increase from by 20°, from 225° to 245°.
At 15psi, the boiling point will increase from 261° to 284°.

The specific heat, however, will decrease from 0.865 to about 0.800, which is about an 8% decrease in the ability to absorb heat.

So, the question is, is it more valuable in this particular application to increase the boiling point from 260° to 284°, when the engine temperature is unlikely ever to go above 220°, or is it more valuable to gain that 8% of cooling that you will lose by using more antifreeze?

- Eric

ps: I added boiling points at 15psi to my earlier post.

MDchanic

Also...

I just looked up WaterWetter.

It's mostly a combination of two alcohol ethers, DiIsopropyl Alcohol Ether and Tri Isopropyl Alcohol DiEther, which are supposed to smooth the flow of coolant over the hot surfaces of the cooling passages, allowing better heat transfer.
It is not designed to affect the boiling point or the specific heat of the coolant.
(It's also got Sodium Molybdate, Tolyltriazole, and PolySiloxane Polymer, which I think are anti-corrosion agents).

The company says it is designed to work best with straight water (the tests they cite claim an 18° temperature reduction when used with straight water, and an 8° reduction with 50/50 antifreeze), so increasing the proportion of antifreeze you use with it would seem to make no sense.
Also note that if your cooling system is already working well, it probably won't do much - the only real thing it might do is to reduce pinging if you have just a little bit of it, by pulling a bit more heat away from the heads.

- Eric

krooser

Virtually every circle track in the country bans the use of anything buy water in the cooling systems because of the dangers of having a car pissing anti-freeze onto the racing surface... a lot of racers use the water wetter. Seems to work.

edzolz

I should have added this is a 60 Bird. Stock engine. The owner (very ****) says the temp needle will go to the "P" in temp in slow traffic. I don't know what that relates to in temperature so I am going to get a laser thermometer and shoot the radiator to get an idea what temp that is. This might be a moot point.

MDchanic

If I recall, that's pretty normal for a 1960 390FE.
(We had a '63 when I was a kid).

- Eric

DeltaPace77

While not automotive, do quite a bit of HVAC chiller work, sometimes with glycol in them. A typical 50/50 mix derates the system capacity by 10%, so can't see how a higher ratio would be any better. Also know a thing about non contact infrared thermometers, as paid $400 bucks for mine. Has 60:1 optics, circular laser sighting, and adjustible refectivity for different surfaces. When you scan accross the room with this, what the sight shows is what you're really getting, not the whole wall, like the cheapo's, with 5:1 optics. Worth keeping in mind, before forking out the cash.

pogo69

I agree here.. distilled water is important