Mixing Different Types of Coolants Can Cause Serious Problems
Why Mixing Different Types of Coolants Is Not Recommended
If you do a search on the topic of mixing different types of coolants you’ll see that some people say that it’s not big deal because the base chemical in all coolants is the same; polyethylene glycol. That was never in dispute. It’s the additive packages that are different and mixing different additive packages together can cause gelling and even accelerate corrosion. Here are some facts I’ve found that support the idea that you should never mix different types of coolants.
1) Some coolant additive packages, when mixed with a different type of coolant can neutralize the anti-corrosion protection of both types, leaving you with NO anti-corrosion protection.
2) Other additive packages can react with one another, actually enabling corrosion, resulting in pitting and rust-through.
3) Still other additive packages can react with one another to form abrasive particulate matter that wears out water pump seals or causing the two coolant to gel and clog the heater core and radiator.
If you switch from a phosphate HOAT PINK coolant to an IAT Green coolant
• The silicate, borate, nitrite or amine containing additives can harm the metals in your engine.
If you switch from a phosphate HOAT blue coolant to an IAT Green coolant
• The silicate, borate, nitrite or amine containing additives can harm the metals in your engine.
If you switch from a phosphate HOAT RED coolant to an IAT Green coolant
The silicate, borate, nitrite or amine containing additives can harm the metals in your engine.
How long does it take for damage to occur when mixing different types of coolant?
It can take 6-months to two years for the damage to occur. This is why people discount the damaging effects of mixing different types of coolants.
What the carmakers say about mixing different types of coolants
Chrysler on mixing different coolants
Chrysler TSB #07-004-12RevA on their new organic acid technology (OAT) coolant for 2013 vehicles. The new coolant is good for 10 years or 150,000 miles. The new coolant is purple. BUT, the bulletin warns about not mixing any other coolants with the purple stuff. And it’s not just so Chrysler can sell you their own brand.
“Chrysler has found that mixing coolants can accelerate corrosion in the engine and cooling system, develop an ammonia smell, and result in debris particles floating in the coolant. That can cause aluminum pipes to turn black, cause engine overheating, and form leaks in the system. If you add any other type of coolant, you MUST flush the entire system and start again with the recommended coolant.
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
Ford on mixing 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.”
“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.”
GM on mixing coolants
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
Toyota on mixing coolants
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.
Valvoline Zerex on mixing coolants
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.
“Mixing coolants of various types can have extensive and expensive consequences. As mentioned above, the mix can solidify, block your engine, and cause overheating, which can, in turn, cause the following problems:
Degraded cylinder heads
Head gasket breakage
Marred hoses
Reduction in vehicle performance
Radiator and water pump corrosion” Valvoline’s website
The anti-corrosion additive packages in different types of coolants can cause damage to the metals in your engine and cooling system.
©, 2022 Rick Muscoplat