What Kind Of Antifreeze To Use In Your Antique Vehicle...

It used to be simple in the old days...all of the antifreeze coolant was basically the same and varied little in price. It usually came down to what was available or what brand was on sale. Not Any More.

Now there are literally dozens of formula's and multiple colors to choose from. So what kind of modern antifreeze should you be using in you antique and more important what kind of antifreeze should you NOT be using in your antique vehicle.

First the Basics...

There are three basic antifreeze technologies in use today, they are as follows....

IAT: Inorganic Acid Technology is the traditional green colored antifreeze that is the closest formula to what antifreeze was prior to the 1980's. The lifespan of traditional coolant is about three to five years. This formula is the antifreeze we want to use in our antique vehicles.

 OAT: Organic Acid Technology is used today because it offers silicate-free protection of all metals, and for a longer period of time: it’s the long life (LLC) or extended life (ELC) coolant and has a service life of five years or 150,000 miles.

Colors in the United States are mostly red and orange, but also green, pink and blue. (modern cooling systems are made up of a variety of different metals and alloys and this formula is designed to not damage the various metal alloys that make up a modern cooling system. This formula has some aggressive cleaning properties that will damage our antique vehicle cooling systems. DO NOT use an OAT formula antifreeze in your antique vehicle.

HOAT: Hybrid Organic Acid Technology. This formula is usually orange, but can also be red or yellow. This formula is a mixture of IAT and OAT, the orange cocktail – and only the orange color -- contains 10 percent recycled coolant. We need to stay away from this formula because is basically a diluted version of the OAT formula.

We need to avoid using both OAT and HOAT type antifreeze.  Even though it is designed for a "longer service life" we shouldn’t use it. The OAT formula includes an inhibitor that attacks silicone compounds that are frequently used in gasket sealants.  In addition, this formula also goes after lead based products like solder and Babbitt material (used in early connecting rod bearings), some yellow metals that may be in cam bearings and radiators, and conventional gasket and seal type packing materials used in some early water pumps.  Your antique vehicle likely contains some, or all of these materials, so using OAT formula antifreeze will eventually result in an expensive headache down the road.  You want to be using only an IAT formula antifreeze in your antique vehicle.

Many early antique vehicles have “open” cooling systems, where the radiator cap doesn’t completely seal the system. This allows for water evaporation, slowly decreasing the amount of water in the cooling system and increasing the amount of antifreeze coolant in the cooling system. The water that is mixed with the antifreeze is what evaporates which can cause you to end up with a higher concentration of antifreeze than the original 50/50 mix. That can cause engine over heating.

Around World War II, automakers began manufacturing cars with a sealed, pressurized cooling system. Not only did that stop evaporation, but for every pound of pressure built into the cooling system the boiling point of the coolant was raised by three degrees (F). As manufacturing quality improved, higher pressures became more common. By the late fifties a seven pound radiator pressure cap was common, which raised the boiling point of the coolant inside the radiator twenty one degrees.

With the addition of coolant recovery tanks in the 1960's life got even better. Now the cooling system was completely sealed from the outside air and dirt and any coolant that boiled over was caught in the coolant over flow tank, which was then drawn back into the radiator as the engine cooled. That solved the problem of air being trapped in the cooling system, and stopped the loss of coolant completely.

Cars and trucks built prior to 1950 were designed to use plain water as the coolant in the summer months and antifreeze only in the winter, in part because there was no such thing as permanent anti freeze in those days. Wood alcohol (methyl alcohol) was the first commercially available antifreeze formula, but its high rate of evaporation (if you did not drain it out in the summer months and replace it with water it would simply evaporate away...) and it's corrosive qualities led to it's eventual replacement by ethylene glycol, which was a year around antifreeze that became the standard up thru the 1980's.

Keep in mind...the antifreeze itself provides no direct cooling benefit. It is there to prevent the water from freezing, and to keep the inside of the cooling system clean so it can work at its most efficient.

That is why using plain distilled water along with a pint of rust inhibitor / water pump lubricant works so well in cars built before 1950. Most early cooling systems were designed to use plain water during the summer and antifreeze in the winter months (hence the name). Typically a early pre 1950's antique vehicle with plain water in the cooling system will run fifteen to twenty degrees cooler that the same antique vehicle with a 50/50 mix of antifreeze and water. Now you know why.

The radiator tubes in antique vehicles built prior to the 1940's are smaller in diameter as are the water passages in the engine block. That is why when you add a 50/50 mixture of modern antifreeze and water to an antique vehicle it often times will run hotter compared to using straight water. The circulation of coolant is slowed down with the addition of the thicker antifreeze.

When shopping for antifreeze, begin by reading the label to make sure it’s an IAT  formula for older cars. You’ll likely find it to be green, the original color for traditional antifreeze. So when you look inside the radiator of your antique vehicle if you see green, chances are your antifreeze is of the IAT formula.

The next question is whether the antifreeze in your classic vehicle is still able to do its job, which is keep the inside of the cooling system clean. Color is a good starting indicator. Remember.... green is good, brown is bad. Brown means some of the the corrosion inhibitors  in your antifreeze formula have broken down and are no longer able to keep the inside of your cooling system clean. Its time for a flush, and fresh antifreeze.

Next up you need to check your freeze protection. You can buy an inexpensive antifreeze tester (at any local auto parts store) and test the antifreeze in your cooling system to determine whether it’s still appropriately diluted for the protection you need. Generally, the best dilution is 50 percent water and 50 percent antifreeze will give you freeze protection down to minus 40 degrees. By taking a sample of the antifreeze from your cooling system you will know for certain what your freeze protection is.

                           

Examples Of Inexpensive Antifreeze Coolant Testers...

You can buy pre-diluted antifreeze for almost the same cost as regular antifreeze. It is the way to go because it is made with the distilled water and you do not have to mix anything, just open the jug and poor it in your cooling system. It will also be easier if you have to add coolant later on, you will always have the proper mixture on hand.




 A good flush at five-year intervals will keep your cooling components clean and working at their optimum potential. It is always a good idea to put a tag somewhere near your radiator cap with the date of the last flush and antifreeze replacement, and your freeze protection number. You should check your coolant level several times during a season to be sure you are not loosing any coolant.

The corrosion inhibitors in antifreeze will break down over time, which is why you should change it periodically.

If you cooling system needs a good cleaning Thermocure is what you need. It is available in the Parts section of the Fifth Avenue website under "cooling". There is also a Garage Tech "Tech Article" on this product an how it works. Just type in Thermocure in the search box on the of the Garage Tech Home page, and the article will magically appear.
 
The search box looks like this...

One other option is to upgrade to Evans Coolant which is a lifetime coolant that freezes at minus 80 and boils at 370 degrees with no pressure in the cooling  system and is non-corrosive. It is more expensive initially as compared to conventional antifreeze, but it is a lifetime coolant so in the long run you get better protection and zero maintaince for the life of the vehicle.

 Evans Coolant is what we have been using in the Great Race cars since 1993 with good success. It is a lifetime coolant you only have to put it in once and it is non-corrosive and works especially well in antique vehicle cooling systems because it requires no pressure in the cooling system to work.

In Summary
Just remember green is good... and be sure to read the back of the antifreeze container carefully.  You want only the IAT formula! 

You want to stay away from the long life formula, the OAT formula and the HOAT formula. Those are formulas for the modern vehicle with the alloy metals and have additives that will damage our early cooling systems. Follow these rules and life will be good!