Which Antifreeze is Right for Your Vehicle?

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Story and Photography by Jim Marotta

Back in the day, no matter which brand you chose, antifreeze was green. The glycol-based formula contained silicates as corrosion inhibitors. You mixed the antifreeze 50/50 with water and poured it in the radiator. As the engine operated, the antifreeze performed its primary duties of carrying heat to the radiator, preventing freezing (hence the name) and protecting against corrosion in the cooling system. You simply changed the antifreeze at the prescribed service interval.
Today, with three types of antifreeze technology in a rainbow of colors, confusion abounds among automotive people and consumers alike as to what color antifreeze is best. The easy part is that most antifreeze manufacturers still make coolant with ethylene glycol (EG), a type of alcohol made from ethane. Manufacturers also make more environmentally friendly versions with less-toxic propylene glycol (PG), a similar compound made from propane.
Evolving Antifreeze
Inorganic Acid Technology (IAT) is the chemical basis for the traditional green antifreeze. IAT contains either EG or PG and is usually fortified with silicate or phosphate additives to make it compatible with metal cooling system components. The generally recommended replacement interval is every three years or 36,000 miles. The owner’s manual or maintenance chart from ChiltonPRO.com and ChiltonDIY.com shows what the vehicle manufacturer recommends for each specific vehicle.

IAT and OAT are two types of antifreeze technology

Inorganic acid technology is the chemical composition for the traditional green or yellow antifreeze (right). Organic acid technology is the orange coolant on the left.

Organic Acid Technology (OAT) is a Long Life Coolant (LLC) / Extended Life Coolant (ELC) widely used in Europe before its introduction in North America. OAT is usually EG. The generally recommended replacement interval is five years or 150,000 miles; find out what the vehicle manufacturer’s recommendations are for your car or truck.

Organic Acid Technology (OAT) is a Long Life Coolant (LLC) / Extended Life Coolant (ELC)

An example of an organic acid technology long life/extended life coolant

Hybrid Organic Acid Technology (HOAT) combines IAT and OAT with nitrites. Antifreeze manufacturers often refer to it as “global,” indicating on the bottle that it meets or exceeds the specification “G-05″ for most vehicles newer than 2002 and “G-11″ or “G-12″ for Volkswagen and Audi. The generally recommended replacement interval is five years or 150,000 miles, always check your vehicle manufacturer’s recommendations for your car or truck.
Why All the Different Coolant Formulations?
In the early 1980′s Ford was working with antifreeze manufacturers to come up with a formulation to meet global needs. European countries had very hard water and since water is 50% of the antifreeze mix, water quality dramatically affects the overall mix. As European manufacturers were abandoning phosphate-based technology because phosphates tend to form scale, Japanese manufacturers were moving away from silicates, which tend to destroy water pump seals.
The first alternate coolants were hybrids combining carboxyl and silicate technologies. Ford started using them after extensive durability testing (more than 40 million fleet test miles on every vehicle platform that Ford had) in the early 1980s. At about the same time, Mercedes and VW were also using hybrid formulations.
In addition to better corrosion inhibitors for the global market, other issues precipitated formula change. Toxicity and environmental concerns are behind the use of PG rather than EG, while the promise of longer-lasting engine protection and less maintenance spur development of the newest formulations, such as Nissan’s blue coolant, which is designed to last ten years or 135,000 miles.
Does Antifreeze Break Down?
Engine antifreeze does break down, forming corrosive organic degradation products. Antifreeze buffering agents inhibit this corrosion. Since most antifreeze leaks out of the vehicle (according to the EPA, only 12% of antifreeze produced in the U.S. is recycled), most systems are “topped off” with fresh antifreeze, extending its life somewhat. How much depends on the type of antifreeze added.
Can You Mix Antifreeze Technologies?
The one universal coolant that all agree on is water. For best performance, water needs a little help. What happens when antifreezes are mixed? A lot of the confusion about mixing coolants stems from early work with carboxyl coolants. In an American Society of Testing and Materials (ASTM) test, mixing IAT and OAT coolants resulted in more corrosion than either antifreeze alone. Subsequent tests revealed a testing error: the corrosive environment occurred because the coolant was too dilute.
It is best to use the same type of coolant originally used in your car or truck, or the vehicle manufacturer’s recommendations. According to industry experts, if you do not know what coolant is in the vehicle and you top off with another brand, nothing bad is going to happen. Only when dilution rates border 50% is the effectiveness of each coolant’s inhibitor package compromised. However, when mixing coolants, the recommended coolant change interval will degrade to that of the shorter-life coolant.
Proper Maintenance is Key
As with anything automotive, proper maintenance is the key to longevity. More important than the type of antifreeze you use is to maintain the cooling system properly by maintaining freeze point protection and proper coolant level. Almost all coolants work best at the ideal freeze point mixture, which for most parts of the country means a 50/50 antifreeze-to-water mixture. At this level, antifreeze protects to -34°F and boil-over protection to 257°F. In addition, maintaining proper freeze point protection ensures corrosion inhibitors are present at intended levels.

A handy tool provides coolant concentrations

Maintaining the cooling system properly by maintaining freeze point protection and proper coolant level is critical. Here a handy tool provides coolant concentrations.

Vehicle manufacturers design cooling systems to operate full of antifreeze. A system that is constantly low on coolant can create an extremely corrosive environment due to the aggressive nature of the vapors of a glycol/water mix. These steam vapors are more corrosive than either fluid by itself. To check your coolant system capacity, simply refer to your vehicle’s capacities chart at ChiltonDIY.com, ChiltonPRO.com, or your owner’s manual.
If you choose to maintain your cooling system yourself, keep in mind that all types of antifreeze are poisonous. Animals and humans can be attracted by its sweet taste. Used coolant is extremely toxic and an environmental hazard, always recycle it properly.
Distilled Water is Best
In almost every part of the country, tap water contains minerals such as magnesium and calcium that can form deposits in a cooling system, especially on the engine’s hottest parts. The water you use to mix the antifreeze is critical. Premixed coolants are mixed at the factory with distilled water. Use distilled water, not tap or filtered water, when you refill any cooling system.

Use distilled water and coolant to maintain the cooling system

A system that is constantly low on coolant can create an extremely corrosive engine environment

Coolant Keeps Working After the Engine Quits
Having the proper coolant level is still important after shutting off the engine. As the coolant stops flowing and the engine temperature increases dramatically, areas of localized boiling can send large shock waves through the engine wreaking havoc on components, especially those made of aluminum.
A subscription to ChiltonDIY or ChiltonPRO, with comprehensive maintenance charts and fluid capacity specifications, will give you all the information you need to keep your cooling system in top shape this summer.
James Marotta A muscle car enthusiast and drag racer, Jim Marotta is a freelance automotive writer with more than 20 years experience in the automotive industry.

17 Responses to “Which Antifreeze is Right for Your Vehicle?”

  1. Bill says:

    I have heard that mixing yellow with green causes a jelling affect
    Is miss and blue comparable with all others ??

    • ChiltonDIY says:

      HI Bill.
      It is best to use the same type of coolant originally used in your car or truck. To be sure follow the vehicle manufacturer recommendations. You can find them in your owner’s manual and in ChiltonDIY when you subscribe for your vehicle.

  2. Dan says:

    Great article, it is always a good idea to use distilled water instead of tap water! Tap water will leave deposits in the engine.

  3. MICHAEL F. CARDAMAN says:

    hv a 89 98 olds regency.

    problem need to know how to replace the engine freezout plugs. The plugs are very hard to get at and working on my back don’t help either. The 2 plugs on the drivers side but need to know what kind of tool needed to remove them.

    If you can help it would be greatly appreciated. been working on my vehicle for 20 yrs,

    tu mike

    • ChiltonDIY says:

      Hi Michael.
      Drill a small hole in the middle of the freeze plug, and then thread a long sheet metal screw into the hole and use a slide hammer to remove the freeze plug. The freeze plug can also be removed using a hammer and a punch. Be careful not to push the plug inside. Cock the freeze plug and pull it out using pliers.

  4. Greg Jantti says:

    Good article as always. Real good information to have with the weather we have had lately. Keep up the good work.

  5. charles emory says:

    Good one.Once green fluid comes out from my antifreeze tank and pour out everywhere. Next day I take my car to Apex specialized automotive in Edmonton and after checking my car they said like you don’t want to worry the raw antifreeze chemicals as they come from Dupont by the tankcar load are clear to light tan in color. Each company differs in their colour to give some unique look.

  6. Lola says:

    My husband has a 2006 Dodge Dakota. He needs to know what kind of antifreeze he can buy that will mix with the antifreeze he has in his truck now?
    Thanks for your help.

    • ChiltonDIY says:

      Hi Lola.
      Check the owner’s manual to see what type of antifreeze is suitable for your husband’s truck. If he doesn’t have the owner’s manual, the 2006 Dakota manual is available free from the Dodge website at: http://www.dodge.com/en/owners/manuals/.
      In addition, many times there is a sticker on the radiator that explains what kind is best.
      On the back of the antifreeze bottle there is a list the vehicles that the brand applies to. However, there isn’t much need to worry, as most major brands of antifreeze are compatible with any other antifreeze (and color) and for all cars and trucks. Just read the label first to make sure.

  7. Ralph says:

    I understand the need for Antifreeze in colder states, but here in Phoenix, sometimes the coldest time of Winter is around 40-50. Well above the freezing poin, but is there another benefit to using antifreeze over water rather than making sure your engine doesn’t freeze up?

    I’d love to hear your response, thanks!

    • ChiltonDIY says:

      Hi Ralph, great question!
      Older cars (and we’re talking 1920s and 30s) got along with just using water in the radiator, because sometimes there were no other options. However, it is like saying drinking plain water will provide a body the bare minimum of what it needs. Why not drink water with minerals and vitamins in it? Same for your car. With the use of a wide range of materials in building engines these days, they need so much more protection than their predecessors did.
      The largest benefit of antifreeze is corrosion prevention. When you have water and iron together with oxygen, rust is a result. Antifreeze provides a protection against rust, something you certainly don’t want inside your engine. As well, antifreeze transfers heat much better and quicker than water alone. It prevents scale buildup (from the chemicals and minerals found in hard water).
      Better suited for your hot climate than plain water, antifreeze is much more stable at high temperatures — meaning it won’t boil or turn to steam as easily as water alone because it raises the boiling point of the mixture.

  8. Nissan 300ZX says:

    Hey there,

    My 300zx is from the 80s. I keep noticing a buildup of gunk in my overflow bottle.

    Any idea if a specific antifreeze will stop this?

    • ChiltonDIY says:

      Hey there.
      Have you ever used a stop-leak product? It’s my personal experience that stop-leak products can cause a gunk build-up in the bottle. If not, you should pull the bottle and clean it out. As to any specific antifreeze stopping it, I can’t say. Personally, if there’s a lot of gunk, I’d drain and flush the system and then refill it with a good quality, name-brand antifreeze in 50-50 antifreeze/water solution.

  9. Bruce says:

    Want to find out about which Antifreeze is good for a 2005 Ford F250 Super Duty Diesel
    Some have said not to use the extended life and the Manufacture mentions Liquid Gold with a stabilizer. Can you shed some light on this as I’m very confused as to what is best to use

    • ChiltonDIY says:

      Hello Bruce.
      There is a science behind the new engine coolants, with the advent of lighter more efficient engines. Heavy-duty diesel OEM (original equipment manufacturer, eg, Ford) recommendations have a wide array of possibilities. In the industrial sector, some OEMs require the use of silicated coolant, while others require silicate-free for heat transfer concerns. And yes, they have testing procedures and special tools. If you’re not sure about the condition and quality of your coolant just change the fluid. Be sure to follow the manufacturer’s recommendations! Vehicle manufacturers are now more than ever using science to get the most out of your vehicle’s cooling system and to optimize your vehicle’s performance.
      We recommend you follow Ford’s specifications to properly maintain your high-technology cooling system.
      Beyond adding the specified coolant, test the level of nitrates periodically as indicated in Ford’s maintenance schedule for your 2005 Ford F250 Super Duty Diesel. Here is an excerpt from Ford’s Power Stroke® Diesel Operating, Maintenance & Care Tips:
      “Engine coolant system nitrite strength should be checked and serviced at the mileage or equivalent hour intervals specified by the maintenance schedule. Check coolant nitrite strength using the 3-Way Antifreeze Test Strip kit Rotunda # 328-00001 to determine if additive is required. If the nitrite strength is between 800 ppm & 300 ppm add 32 fl. oz. (946 mL) of Supplemental Coolant Additive Motorcraft VC-8 or equivalent. If nitrite strength is below 300 ppm flush & refill engine coolant (refer to Motorcraft Premium Gold Engine Coolant Change Record) – Do not add Supplemental Coolant Additive if flush and refill is required.”
      You’ll find Ford’s diesel maintenance tips, owner’s manuals and more for your 2005 Ford F250 Super Duty Diesel at: https://owner.ford.com/servlet/ContentServer?pagename=Owner/Page/OwnerGuidePageVehicleLookup&BackToLogin=Owner/Page/OwnerGuidePage&ord=9276196
      Stay abreast of changes at the Ford owner’s site and with your ChiltonDIY subscription for easy-search technical service bulletins (TSBs; where Ford informs its dealers of changes and issues) and Recalls.

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