Using /or mixing yellow, green antifreeze

[ArtJ]

Is there any issue with mixing the yellowish anti freeze with the green?

Thanks and Regards

Art

[ndutton]

Found this online: (sorry for the length)

For the past several years, vehicle manufacturers have introduced a variety of new extended-life coolants. Each seems to have its own colors. Each formula considers corrosion protection, service life and chemical compatibility. We have green coolants, red coolants, blue coolants, yellow coolants, even pink coolants. The closer we look at this diversity, the more confusing it becomes.

Groups of Coolants
Let us begin to sort this out by pointing out the three principal groups of coolants. We will not define every possible coolant and its corresponding color. Indeed, yellow coolants may have very different compositions. A blue coolant may have the same formula as a red coolant. The three basic divisions include the following:

Group 1 - the original glycol-based “green” antifreeze we are all familiar with. They have quick-acting silicate and phosphate corrosion inhibitors that do a good job inhibiting corrosion on both iron and aluminum surfaces. This familiar green liquid has proven its worth in all the temperature extremes of North America. Virtually any vehicle can use this fluid. Why not make this the universal coolant? You could, and maybe we have, but the corrosion inhibitors have a very short life and the antifreeze must be changed every other year or every 30,000 miles. If the customer fails to perform this maintenance, then expensive radiator, heater core and pump replacements soon follow. Unfortunately, many motorists do not keep up with maintenance, even with encouragement from their mechanics.

Group 2 – coolants based on the organic acid technology (OAT). They contain 2-ethylhexanoic-acid or 2-EHA and other organic acids, but no silicates or phosphates. This formula gives longer life, thus replacing the short-lived silicates and phosphates. Many colors reside in this group. General Motor’s OAT-based DexCool is orange. Volkswagen-Audi has the same formula, but it is pink. Honda has one coolant dyed a dark green, which looks almost black when it is dirty. The corrosion inhibitors in this group are slower acting, but longer lasting. Five years, or 150,000-mile intervals are often recommended in this group of coolants.

Group 3 - the group of hybrid OAT coolants called G-05. They do not have 2-EHA but use other organic acids and add a little silicate. Silicate is desired because it provides quick-acting protection for aluminum surfaces. Silicate will also repair minor surface defects. Chrysler, Ford, and many European manufacturers are using these hybrid OATs.

Time for a Change
OK, there are lots of coolants and different colors out there. Do you have to replace or can you top off one coolant with another? A truly universal coolant would help matters greatly, Providing the ability to use one coolant for all purposes. To partially refill any color of coolant with a universal one would be a great asset. Its existence would totally dominate the aftermarket in a short time.

In my opinion, there is one true universal coolant - the original green stuff. It is the cheapest, it protects and even repairs minor aluminum flaws, and the only inconvenience is its short lifespan (offset by its low cost) with the semiyearly drain and refill. In your local parts store, you will find Group 2 OAT coolant being advertised as universal in its ability to mix with other coolants. This is true, it will mix. But the 150,000-mile advantage deteriorates if you mix it with Group 1 or Group 3. Why pay a higher price to mix red with green or another color only to lose its ability to provide extended life?

OAT coolants are not the best choice for systems that have traditional brass/copper radiators and heater cores. In the past, I replaced high-priced aluminum radiators with cheaper copper ones, and neglected to remove all of the OAT coolant and replace it with green. I am sure the copper did not last as long as it should have with OAT antifreeze.

A Word of Advice
My rules for the present are this: Stick with the green and change it every year. You will likely forget once in a while, so that will still keep you on the better side of every other year or 30,000 miles. Green is substantially cheaper than OAT and can be mixed with anything without penalty. Use the recommended 50/50 water-coolant mix unless you live in extreme cold situations or have corrosion issues in your system.

The aftermarket parts industry is good about sorting the good from the bad and they are working toward universal coolants; one coolant is to take the place of all others. The part stores are motivated by floor space and simplicity in their recommendations to their customers. So if you see the higher priced stuff being touted as the universal coolant, remember its deterioration when mixed with any other coolant, and its higher cost. Stay with the green.

I would be curious about the coolant choices in manufacturing and industrial situations. There are service companies within the oil field community whose sole business is cleaning and repairing the large brass/copper heat exchangers and radiators.

The industry will eventually come up with a long-life, brass/copper safe, and totally mixable universal coolant. I wonder what color it will be.

[ArtJ]

Thanks Neil
A follow on question occurs to me - Is it bad to have the coolant too pure, rather
than 50 50 mix. I recall one of the attendants at a "quick oil change " place
insisting that my car antifreeze was no good because all the little balls were floating.

Thanks great article

Art

[ndutton]

50-50 is the way to go.

My understanding is straight antifreeze does not conduct heat as efficiently and the freezing point is 20 degrees higher.

[msmith10]

On the 50-50 mix, Neil is right. Freezing point of the mix is lower, boiling point higher than straight.

[ArtJ]

On the 50-50 mix, Neil is right. Freezing point of the mix is lower, boiling point higher than straight.

Just curious, do you guys know scientifically wny this occurs? Seems counter-intuitive.

Best Regards

[marthur]

Here is the high school chemistry explanation of freezing point depression:

To freeze, water or glycol molecules must form crystals. At the freezing point, these crystals form and break up all the time. If the mixture, the crystals are not as "stable" and break up easier, so the temperature has to be lower for them to stick together. This is because the water or glycol molecules will not "pack" as well into the crystal lattice. A lower temperature makes it harder for crystals to break up, so the freezing point is depressed.

In fact, a mixture of water and any substance will depress the freezing point. It just turns out that glycol works better than most other stuff.

On a side note, I use vodka or grain alcohol to winterize my water tank on the boat because I prefer vodka residue to anti-freeze.


Here is the slightly more advanced version: At the freezing point, ice and water coexist. The melting ice is exactly balanced by freezing liquid molecule. Chemists say that "The chemical potentials of the two phases are equal under these conditions" and they write it like this:

µice = µpure water

where the chemical potentials are the molar Gibbs free energies.

But, when you make a mixture, the chemical potential for the liquid is lower. The formula for this effect in water looks like this:

µ of the solution water = µ of pure water + RT ln( x)

R = gas law constant
T = temperature
x = mole fraction of water in the solution
ln = natural log function

It would look the same for the pure glycol.

Note that the natural log of a fraction is negative, and when you make a solution the mole fraction of water (or glycol) is negative. Thus you have to lower the temperature to establish the equilibrium with the ice crystals.

The next question you will ask is why does the chemical potential decrease in a solution? The short answer is that the entropy changes. I won't go into that because I would have to look it up to explain it in any detail : )

Boiling points are changed for a very similar reasons.

[thatch]

"The obvious answer"

Marthur,
I'm not quite sure what you just said, but my answer would have to be, "I'll drink to that"
Tom

[Carl-T705]

Marthur, Do you rinse the tank out in the spring or just add some fruit juice??
I once bought antifreeze I thought was premixed, it was not, I ran this stuff in a 10 gallon cooling system on a diesel truck and the freeze point was -67* F. I don't think the freeze point suffered at all. Changing antifreeze every year is a waste of money and not envio-friendly. They sell test strips to monitor AF and additives to keep it within specs. IMHO.
I use some special coolant in my racecars and for the life of me I can't think of the name but it has no water in it at all, actually water contaminates it. It cost $25.00/gal and raises the boiling point to 245*F at zero pressure. The company suggest you run the engine temp at over 200*. It will not draw away from the hot metal like water base coolant does, ( just thought of it.... Evans coolant). I've run this engine at over 200* and you would be amazed at how quiet the engine runs at this temp, quiets right out and sounds like a sewing machine operating. In the instructions if converting over a system it says to totally block off the radiator and run the engine up to 220* with the radiator cap off to boil the water out of the system.