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 different 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, 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. Always recycle antifreeze 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.

63 responses to “Which Antifreeze is Right for Your Vehicle?”

  1. zephod says:

    Where do I get concentrated antifreeze that I can add 1+20? My cooling system needs 17 gallons of the stuff!

  2. Art says:

    Awesome site great info

  3. […] year 36k miles. Here is a good article that convinced me to use the "OAT" based stuff http://blog.chiltondiy.com/2013/06/w…ge-1/#comments I'm not sure what the Purists on this forum think but since I had a whole new Cooling system […]

  4. Zak says:


    I’m trying to figure out which coolant for my VW Jetta Wagon should be used. I think its the G12 which is an orangish/pink color but someone else has told me to get the “purple” one. Which is also for sale at my Napa store.

    My Mechanic has been using the G12 “orange” one but before i go and tell them they are using the wrong one or not i want to be certain im not getting bad information.

    Is there anyway you can help me clarify this? What im reading online is that the purple is the newer version but that the orange isn’t “wrong” per se but just older version.

    So my end question is should i be flushing my system with the old and tell/ask them to get the purple in and install that in my car?


    • ChiltonDIY says:

      Zak, the “purple” one your friend has told you about is the latest Audi/VW-approved coolant, the G13. The specification or type of VW coolant required for your particular model can be found stamped on the coolant expansion tank (eg, G13 or G12) as well as in the owner’s manual (look under the coolant section). It’s also good to note the color of your coolant (eg, pink or purple). Even though the latest G13 coolant is backward compatible, we strongly recommend thoroughly flushing your cooling system when upgrading to a different type of coolant. This maintains the purity of the cooling system and won’t lead to a sludge that will damage ancillary parts. To answer your question, it doesn’t really matter what coolant you use, G12 or G13, but what does matter is that you don’t mix different coolants when topping off or flushing out the system.

  5. Bow guy says:

    Hi I have a bmw 328i 1999, what would be the best antifreeze for my vehicle ?

    • ChiltonDIY says:

      According to BMW, for best results, use genuine BMW “blue” antifreeze/coolant. It is silicate and phosphate free. You can find it at your local BMW dealership or from a variety of sellers online.

      • RiponJim says:

        Also Rowe makes the oe coolant for BMW and MB – p/n 21066-998-0:
        OE Notes Hightec Antifreeze AN (Blue) – Supplied as First Equipment Fill or as Original Equipment Service (OES) – Meets
        Specifications: ASTM D3306/D4985, AFNOR NF R 15-601, BS 6580 ,SAE J1034, BMW N60069.0, DEUTZ, MAN 324 NF/Pritader, MB
        325.0, MTU MTL 5048, Opel/GM B 040 0240, VW TL 774-C (G11) – Mixture: Concentrate Full Strength – Requires 50/50 mix with
        purified water. 1 US Gallon / Case = 4 Gallon Bottles.
        ROWE Hightec AN Coolant (G11) – 1 Gallon

  6. Jake says:

    What is the best coolant to use in a 2004 volvo c70 turbo? Some people tell me that I need to use the g12 and some say to just use the regular green coolant.Which do you recommend is the best?

    • ChiltonDIY says:

      Hello Jake!
      A hybrid organic acid technology coolant is called a HOAT and should be used in modern diesel engines and other turbos and is in all BMW and Mercedes. (BMW coolant and Volvo coolant are exactly the same).
      The HOAT used in Volvos has sebacic acid and some silicates in addition to the normal OAT (organic acid technology) ingredient of 2-EHA. These are the chemicals that make a difference in keeping it from boiling over and repairing damage to aluminum at a molecular level. The G12 (and G12++) are OAT products, while Zerex G-05 is a HOAT mix.

  7. NAPA Guy says:

    Your car came with G11 but I agree that you should upgrade to G12 or G13 newer technology. G13 is glycerin based and when manufactured puts out like 11% less emissions into the air and is based on recycled and renewable raw materials like biodiesel.

    Just do not mix them with the G11 which is glycol based, from mineral oil.

  8. mike daniels says:

    having trusted the label claiming to be compatible with all makes / years / ,models car and all color antifreeze , i used the green 5 yr 50000 mile stuff and after a couple years have no clue what i used when nor the percentage of which is in the cars.91 lumina 3.1 and 3100 1994 beretta , which should i use ? the green silicate as was original fill or the Prestone 5/ 500000 green one that claims compatibility? I must do a dilution and chemical flush as on one car a regular backflush is extremely difficult ..so after i chemical flush and dilute as far as possible , which coolant should i use ? Please set me on the right path .

  9. mike daniels says:

    thanks –i tried comment on the forum sight you posted it to and i registered and signed in but cannot seem to post ..i will be monitoring both pages ..thanks.

  10. ChiltonDIY says:

    Hi Mike, thanks for joining us at the forum! Once you have signed on as a user you can make comments.

    To comment on a forum question, first select the topic or question and click on it.

  11. ChiltonDIY says:

    Mike, when the question or discussion topic opens up, you’ll see the thread, starting with the original comment.

    Scroll down and you’ll see a text box after each comment. The example shows the first text box.

    Find the comment you want to reply to and begin typing in the box. Click the “reply” button to post your comment.

  12. Varun says:

    What coolant should i use for a 2003 Mercedes Benz C200 Kompressor elegance. the coolant in the tank at the moment is green.

  13. Chris says:

    You didn’t answer the question that you typed at the very top of the page. “Which antifreeze is right for your vehicle?” is a question that should be followed with something like “For [such and such make/model/year range], the [green/orange/red] is the coolant you should use.” But instead, you wrote a fucking essay on the history and chemical makeup of different coolants. Nothing in this article answered the question that I typed into google, which incidentally was almost the exact same question you headlined this article with, and yet here I am 10 minutes later and I don’t know, because you didn’t tell me, which means that this was really a waste of time. Dammit.

  14. Joe says:

    My 2009 Nissan Sentra has the green LLC with a manufacturer’s replacement schedule at 60,000 miles and then every 30,000 miles. The dealer did this work at a very reasonable price, but now no longer sells Nissan. The new dealer quoted a ridiculous price of around $180. Thank you Nissan!

  15. Draining and refilling the coolant is one of the easier maintenance tasks you can do on most vehicles. In addition to saving money, doing your own maintenance allows you to monitor the health of your vehicle.
    Read on for a procedure to refill the coolant without using a bleed tool: How to Refill the Coolant/ Antifreeze without using a Bleed Tool.

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