Groups of Coolants — Selecting the Right Antifreeze

I have always encouraged my customers to call me when they have problems on the road. I can calm, advise and perhaps solve their automotive challenges over the phone.

Recently, I got an angry phone call from one of my favorite customers.

“My transmission is leaking,” he said, with frustration and anger in his voice. “I am on a trip, and my car is broken down with an overheating engine.”

I questioned him and determined that his engine was, in fact, running hot. I asked him how he knew it was the transmission.

“You serviced it recently,” he replied. “The same pink fluid you put in it is now running out on the ground. I saw you put it in, and it is the same color, transparent pink. So it must be the transmission leaking that caused the car to run hot.”

After assuring him that a slipping transmission could possibly be the problem, but it was likely something else, I directed him toward the coolant reservoir under the hood. It was empty, but there was just enough residue to confirm that what he thought was transmission fluid was actually engine coolant.

I contacted a garage in the city where he was vacationing and got him towed. At the garage, they replaced his coolant bypass hose and the water pump.

His comment was, “I thought all antifreeze was green.”

Proper Names

For our purposes, the titles of Antifreeze and Coolant will be interchangeable, as indeed they are in my business. Originally, antifreeze was the preferred term because that was its main purpose.

Keeping the water in an engine block from freezing was the only reason for using anything but water. As engines and their accessories mature, heat transfer demands become more important; therefore, the word coolant was used more often.

Today, coolants come in many colors, and each signifies a purpose. It can be confusing to have special-needs coolants that can be identified by their color when the color is not an industry standard.

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 and 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 of 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 in a way 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

These are coolants based on 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.

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 is 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 extremely cold environments 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.