Rick's Free Auto Repair Advice

Can you mix antifreeze colors

Does it matter if you mix antifreeze colors?

I always see questions from forum users who ask, “does it matter if you mix antifreeze colors?, or Can you mix antifreeze colors?” Their question is always followed up with, “The bottle of Prestone says it’s compatible with all types of antifreeze.” Well, kinda. But here’s where you get into trouble when mixing different colors of antifreeze or different types of antifreeze. Car makers select an antifreeze chemistry based on the types of components (fittings, seals, tubing) of each particular cooling system’s internal components. Car makers use more plastic fittings in late model engines and the antifreeze base chemistry and additives must be compatible with the different plastics and seal materials. Even though some OEMs use the same type of chemistry, the chemical concentration and the formulations are extremely dissimilar. Different coolants may not adequately protect all types of engine, radiator, heater core, and other cooling system materials.

Here’s what you need to know about the different types of antifreeze

Antifreeze does several jobs. Of course it must prevent the coolant from freezing in winter. But its other main job is to prevent corrosion throughout your cooling system. Modern cooling systems contain several different metals. The radiator can be made with aluminum or copper. The cooling lines can be made from steel or aluminum. The heater core is usually made from copper or aluminum. The water pump is made with several materials, magnesium casting, steel impeller, and steel bearings. When dissimilar metals are connected by an electrolyte like antifreeze or water, you get galvanic action. Electrons transfer from one metal to another, creating thin spots and pinhole leaks. Antifreeze contain anti-electrolysis additives to prevent galvanic action. But there are several ways to accomplish this corrosion protection.

Inorganic Additive Technology (IAT)

This is the conventional green antifreeze that uses silicate or phosphate inhibitor technology. Silicate and phosphate plate a deposit of material on all components throughout the cooling system to form a protective layer. This process is called “passivating” and the plating prevents electrolysis. Silicate and phosphate coat internal parts rapidly, so your system is protected shortly after a coolant flush.

Organic Acid Technology (OAT)

These coolants use organic acid to eliminate electrolysis. Most are phosphate, borate, and silicate free. Organic acid technology reacts chemically with the metal surfaces to prevent electrolysis. This process takes much longer than IAT. If your vehicle used IAT and you flush and fill with OAT, it takes several thousand miles to establish corrosion protection.

Hybrid Organic Acid Technology (HOAT)

These coolants use a combination of silicate & organic acid

Phosphate Hybrid Organic Acid Technology (PHOAT)

These coolants use a combination of phosphate & organic acid

Coolant corrosion additives for different metals

Phosphate is for IRON protection and pH control
Borate is for IRON protection and pH control
Silicate is for Aluminum corrosion protection
Nitrate is for cast iron and steel protection
Mercaptobenzothiazole (MBT) and Tolytriazole (TT) are best for Copper and Brass Protection
Block Polymers are for Defoamant and Scale and Deposit Control
Potassium Soap of Dibasic Carboxylic Acid for Iron, Solder and Aluminum Protection
Potassium Soap of Monobasic Carboxylic Acid for Aluminum and Iron (w/sebacate) Protection
Nitrite for Cast Iron and Steel Protection
Molybdate for Iron Corrosion Protection (w/nitrite)
Tolytriazole for Copper Corrosion Protection
Modified Silicone for Defoamant

What about Universal Antifreeze or Antifreeze that’s compatible with all types?

Gates, maker of coolant hoses, fittings, and water pumps publishes several bulletins for technicians regarding the practice of mixing different types of coolants. Here’s a warning from Gates Bulletin TT002-13:

Gates warning about mixing different coolant types

“Corrosion inhibitors and additives from one coolant can negate the effects of inhibitors in another coolant. Corrosion can take over well before 5000 miles and then the car is back in the shop with a leaking water pump and clogged radiator and heater core.

Topping off the system is a common practice at many shops. This can begin the corrosion process unless the proper coolant is used. Most shops use Universal antifreeze because it says on the container that it is OK to mix with any color coolant. But, take a look at the back of the bottle. They all either recommend or require a drain, flush and fill to experience the expected corrosion protection.”

Mixing different types of antifreezes can reduce their corrosion protection and can actually lead to corrosion problems. Engine manufacturers recommend a 10% limit on mixing coolant types. If you add more than 10%, it is recommended that you flush the system and replace the antifreeze—EET Corporation

Gates Bulletin TT002-13

Then there are these manufacturer quotes from Aftermarket Business, July 2006

Excerpts from: An antifreeze antidote

Ford warning about mixing different coolant types

“John Conville, a coolant expert at Ford Motor Co., emphasizes that Ford does not recommend the use of any specific aftermarket coolants in their vehicles (unless approved). “…the only aftermarket coolants that Ford recommends are the appropriate Motorcraft brand engine coolants.” With the use of non-approved coolants, Ford is concerned about “corrosion of metals and incompatibility with some of the polymeric materials we use in our vehicles.”

Chrysler warning about mixing different coolant types

Chrysler states: “Mixing of coolants other than those specified (i.e. non-HOAT) may result in engine damage that may not be covered under the new vehicle warranty, and decreased corrosion protection. If a non-HOAT coolant is introduced to the cooling system in an emergency, it should be replaced with the specified coolant as soon as possible.” An antifreeze antidote, Aftermarket Business, July 2006

Ed Eaton, chief engineer at Amalgatech, a professional automotive fluids and heat exchange independent testing lab, explains that Ford and DaimlerChrysler both use Valvoline G-05®, a European-style hybrid formula. Most Japanese automakers use a hybrid formula too, but it is vastly different. And General Motors uses DEX-COOL®, an organic acid technology (OAT) formulation.

Toyota warning about mixing different coolant types

Toyota, which has long life and super long life non-silicated products, too, does not advocate the use of non-genuine antifreeze/coolants. Toyota Motor Sales’ Bill Kwong in product communications explains that other formulas tested didn’t provide the same performance. “Evaluations of competitive formulations have been made in simulation and field tests, showing (Toyota’s) product superior in water pump seal protection, leakage and deposit formation.” It’s uncertain whether he’s referring to competitive OEM or aftermarket formulas.

Ford articulated that the automaker doesn’t believe a universal formula could work properly in all vehicles by distributing a Q&A document to their dealer network and other public channels. It says, “Due to the complexity of cooling systems, no one coolant has been proven to work in all vehicles,” and “use of non-approved ‘universal’ engine coolants may lead to eventual engine damage or failure. Problems caused by the use of non-approved ‘universal’ coolants may not arise immediately but may occur over longer periods of time due to additive compatibility issues.” Conville says they do not have specific test results on such coolants because “there are many different coolants in the North American aftermarket and Ford does not have the resources to test them all.”

Some aftermarket chemical makers share stances similar to the OEMs. The Valvoline Co., a division of Ashland Inc. and the maker of Zerex® antifreeze products, recommends following the OEM’s formulation suggestions. Valvoline’s David Turcotte, technical director of the company’s Technology and Product Development division, believes that in some instances of damage, “cause and effect isn’t always obvious.” Other than the apparent compromises in performance, much of the physical damage caused by improper coolant use is not noticed until the cooling system is dismantled, said Turcotte at a recent product presentation.

GM warning about coolant types

Consumers need to be careful of what they buy because it’s a chemical manufacturer’s job to sell coolant and they “enhance their ability to sell coolant by making claims that a coolant is compatible with all the carmakers. We know from the formula that some of them don’t work.”   GM spokesperson Lockwood

“Problems with corrosion, oxidation and electrolysis in cooling systems usually occur when the coolant has lost its protective additives and/or becomes electrically conductive. These problems occur as often with the approved application-specific coolants as they do with aftermarket products.”

What antifreeze should you use?

Aftermarket “Universal” coolants sell for about $10/gallon. Genuine OEM coolant sells for around $23/gallon. Most cooling systems require no more than two gallons. So using the OEM antifreeze means a trip to the dealer and an extra cost of around $20. Replacing a heater core due to premature corrosion can cost upwards of $1,500 and an average radiator replacement runs about $450. Water pump replacements can easily cost $400.

To me, it’s a no brainer. But if you still have doubts, do the math.

© 2015 Rick Muscoplat



Posted on by Rick Muscoplat

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