What are the Different Types of Antifreeze and Can I Mix Them?

Recently we discussed the benefits of antifreeze in our “Do I need Antifreeze in Warm Weather?” article. We explained that antifreeze not only lowers the freezing point of the water in your cooling system it also raises the boiling point and helps inhibit corrosion. However, there was one critical item we did not discuss: the different types of antifreeze. Before you grab that jug of green liquid to pour in your system, you better make sure it’s the same as what’s there already.

Some General Facts about Antifreeze

Before we get into making sure you have the right antifreeze in your system, let’s take a look at some general information about antifreeze.

  1. Automotive antifreeze has traditionally been made with ethylene glycol and Inorganic Acid Technology (IAT) corrosion inhibitors since 1926.
  2. American vehicles have traditionally been designed to use antifreeze with silicates and phosphates as corrosion inhibitors.
  3. European vehicles have traditionally used antifreeze that does not use phosphates.
  4. Japanese vehicles have traditionally used antifreeze that does not use silicates.
  5. Newer corrosion inhibitor technology includes Organic Acid Technology (OAT) and Hybrid Organic Acid Technology (HOAT). Both may be referred to as “extended life” antifreeze and were introduced in the 1990′s.
  6. IAT antifreeze has a 2 year or 30,000 mile service life, where OAT and HOAT have a 5 year or 150,000 mile service life.
  7. OAT based antifreeze is not compatible with IAT antifreeze; although, some HOAT formulas claim compatibility with certain OAT formulas or IAT formulas.
  8. OAT and HOAT antifreeze is designed for use in aluminum radiators and components.
  9. Antifreeze is dyed to whatever color the manufacturer chooses and may help to distinguish the type of antifreeze (IAT, OAT or HOAT) or may be used to market variations of antifreeze formulas within a brand.

How Do I Know Which Antifreeze is Right for My Vehicle?

Given that there is now a wide variety of antifreeze available, it is easy to get confused about which one is correct for your vehicle. Here are are a few questions to ask yourself before buying antifreeze.

  • Does my vehicle have antique parts like a Copper/Brass radiator? If you do, then the only antifreeze you should use is the traditional, IAT based formula. The new OAT formulas do not have the corrosion inhibitors that will protect copper/brass components since they were designed for modern aluminum components.
  • What does my vehicle’s manufacturer recommend? Check the manual or call the dealership and make sure. Modern vehicles typically use the OAT based products.
  • What’s in my radiator now? Some mechanics have been known to drain out and replace the factory supplied OAT based antifreeze with traditional IAT due to performance concerns about one of the first OAT formulas used called DEX-COOL®. If you took your vehicle to a mechanic who recommended replacing the coolant with a traditional formula, make sure you know which formula is in your system.
  • What color antifreeze is in my vehicle already? The color of your coolant may be a first indicator that you have something other than traditional antifreeze in your vehicle; however, NEVER RELY ON THE COLOR TO DETERMINE WHAT TYPE OF ANTIFREEZE YOU NEED! There are no standardized rules for manufacturers about what colors to use for their formulas. If you buy a jug of antifreeze and the color is different than what is in your vehicle already, take it as a sign to double check yourself before you mix the two together but don’t rely on matching colors as guaranteed compatibility.

Can I Mix the Formulas Together? Is it Really that Bad?

You should not mix OAT based formulas with IAT formulas. The result is typically turning your coolant into sludge due to a chemical reaction. Keep in mind, OAT based formulas are still a developing technology. There are some “universal” formulas that claim compatibility with other IAT and OAT formulas, but the only safe bet is to use the same formula that is already in your vehicle. This may change as the OAT based formulas continue to develop; however, always err on the side of caution and use the same type of formula that the manufacturer recommends.

What Should I Do if I Do Mix Them?

Your best bet is to drain and flush your coolant system as soon as possible. The longer two different formulas are allowed to circulate through your system, the more particles and sludge that can build up. Again, play it safe and drain the system, flush it with coolant, drain it again, and repeat if you still see particles coming out. When you finally have it flushed, replace the coolant with what your manufacturer recommends. At the end of the day, the system was designed to work with the coolant they put in it.
If you have concerns about your cooling system and need some extra help, give our service staff a call at 1-800-223-4299. They can help you determine what you need to do to keep your vehicle in good shape.

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