Antifreeze: Red (OAT type)

[V Mad]

I was talking today to the manager of a reputable motor factor outlet about antifreeze. I asked what he knew about the different types (traditional Ethylene Glycol vs the newer OAT types), their suitability for different types of car and their compatibility if mixed.

He stated that if you mix the two types you will get a gel sludge that blocks the coolant passages, and will need to replace the radiator and power flush out the engine.

Is this scaremongering or fact based?

I think the risk is low, but it's worth taking the precaution of never mxixing the two types just in case. Here are a couple of paragraphs from an AA website you may find interesting ( my highlights not theirs): http://www.aa-academy.com/asp/info.asp?id=72

"Silicate levels in G11 antifreezes vary. The level used to be as high as 1000 ppm, but this has been reduced to around 250 ppm.At this level there shouldn’t be any precipitation of silicates if mixed with another type of antifreeze.You may have heard of, or seen, cases of horrible green/yellow gel/sludge in the radiator if different types of antifreeze are mixed. BMW still favour a conventional high silicone green anti-freeze.

A combustion gas leak (resulting from head gasket failure) will deplete the corrosion inhibitors as the carbon dioxide dissolves in the coolant and forms carbonic acid.

Now the risk of silicate precipitation has been reduced there is still an issue with different corrosion inhibitor packages which can work against each other."

[Kevin Garrod]

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I'm using Halfords pink antifreeze which i believe is an OAT type. I did flush the system out as best as I could first and I've had no problems so far, no signs of any sludge or anything. I'm planning on flushing the block and replacing with the same type of antifreeze later in the year..but that is part of another story.

[StagnJag]

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When I bought my Stag the antifreeze was this colour :shock::shock::shock::shock::shock: - see yellow container. And no it isn't oil!!!! Anyone know what type of Antifreeze it was :P?

I suspect it was the result of mixing incompatible types of Antifreeze. It was black, but it wasn't at all sludgy! It is a much more healthy colour now. (Halfords pink stuff!)

Dave

[Andrew S]

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V Mad wrote:

I was talking today to the manager of a reputable motor factor outlet about antifreeze. I asked what he knew about the different types (traditional Ethylene Glycol vs the newer OAT types), their suitability for different types of car and their compatibility if mixed.

He stated that if you mix the two types you will get a gel sludge that blocks the coolant passages, and will need to replace the radiator and power flush out the engine.

Is this scaremongering or fact based?

I think the risk is low, but it's worth taking the precaution of never mixing the two types just in case. Here are a couple of paragraphs from an AA website you may find interesting ( my highlights not theirs): http://www.aa-academy.com/asp/info.asp?id=72

"Silicate levels in G11 antifreezes vary. The level used to be as high as 1000 ppm, but this has been reduced to around 250 ppm.At this level there shouldn’t be any precipitation of silicates if mixed with another type of antifreeze.You may have heard of, or seen, cases of horrible green/yellow gel/sludge in the radiator if different types of antifreeze are mixed. BMW still favour a conventional high silicone green anti-freeze.
A combustion gas leak (resulting from head gasket failure) will deplete the corrosion inhibitors as the carbon dioxide dissolves in the coolant and forms carbonic acid.
Now the risk of silicate precipitation has been reduced there is still an issue with different corrosion inhibitor packages which can work against each other."

Hi V Mad

Its true and I know someone who had this gel and blocked their radiator. To test this theory for myself I took a large glass and filled it full of pink and then dropped one teaspoon of green in. That was enough proof for me as it formed globules like oil in water. I have now converted to pink since my engine rebuild but wouldn't have had unless I knew I had completely flushed the system with a chemical.

Hope this helps

Andrew

[V Mad]

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Andrew, the oily globules is obvious signs of incompatibilty but no indication of harmful of gel/sludge. I wondered if you heated it to 100C, and put it in the blender (if you want to accelerate a divorce) whether you could cause a gel to form?

I would not choose to change to the new OAT type for classic engines as there may be a risk to seals/gaskets. There was a lawsuit in the USA GM vs Dex-Cool (OAT) which claims it has caused gasket failures on certain GM cars (settled out of court). I consider it unproven c.f. the old 'blue' or 'green' ethylene glycol types.

[Pommie Stag]

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Vmad,

Good warning I had a chat with Peter at LD parts when I subscribed to there cooling article I asked what happened if you mixed the two.

he was of the same opinion don't especially on our Stag's Black sludge and poor waterways recipe for disaster:shock:

[marshman]

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Having looked into this as well I tend to agree with vmads post. The GM case was confused as they also introduced other changes to some components in their cooling systems at the same time - which contributed to the reported problems.

I would also like to point out that NOTall red antifreeze is of the OAT type. I have someUnipart stuff in a 20 litre drum bought recently. I have checked and double checked and it is the traditional Ehtylene Glycol type. So don't panic if your is red.

As with most things, oils, anti-freeze, brake fluids, tyres, shockabsorbers etc.Stick to what you've got and what works for you. Top up/renew with the same stuff/type/brand etc. and you shouldn't go far wrong. If you do need to change the basic type then get rid of all the old stuff first - common sense really - most pepole (I hope) wouldn't even consider replacing just one old standard shock absorber on one side of the car with a brand new Koni or similar type, they would at least change the pair if not all four - the fluids in a car should be treated the same.

Roger

[V Mad]

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Most people already know, but I think its worth also mentioning that the engine block holds a lot of coolant, and to remember, if changing between different types of antifreeze to drain the block both sides as well as the radiator.