Why isn't Polyethylene Glycol standard?

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As someone who tries to be environmentally conscious when possible, I started dabbling around and looking into the differences between Polyethylene and Ethylene coolants. Yes I know it's a closed system and environmental exposure is minimal. However, in the U.S. alone there are roughly 250mm registered vehicles with 270mm registered drivers. Let's assume most coolant systems hold an average of 5gal, we're talking about 1.25B gallons of coolant on roadways. If annually there are 6mm accidents, and let's say 40% end up with a cracked radiator, we're looking at roughly 500mm gallons of spilled coolant. Based on what I can find, there doesn't seem to be a difference between the two from a compatibility standpoint. When it comes to practicality, there are some physical differences between the two with regards to heat transfer and freeze rating. But even then, it's not that different. For example, Prestone Extended Life has a freeze rating of -34*F and boilover rating of 265*F in a 50/50 mixture. Meanwhile, Prestone LowTox has a freeze rating of -26*F and a boilover rating of 229*F in a 50/50 mixture.
 
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It's pretty simple performance wise it's pretty much a wash, so ethylene glycol became the standard in cars as it's easier and cheaper to manufacture. The toxicity issue is a non-issue today as all regular ethylene glycol coolant sold in the US since 2013 (and earlier in some states) comes with a bittering agent added to avoid poisoning animals. https://www.avma.org/javma-news/2013-02-15/antifreeze-manufacturers-agree-bittering-agent-addition#:~:text=Antifreeze%20and%20engine%20coolant%20are,appeals%20to%20animals%20and%20children.&text=Seventeen%20states%20currently%20require%20adding,ethylene%20glycol%2C%20usually%20denatonium%20benzoate.
 
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I was under the impression from an article I read ages ago that there is bacteria in the soil that does a fairly handy job 'eating' up most kinds of coolant types these days. I also don't think they use much if any lead in the radiators to make heavy metals an issue either.
 
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Originally Posted by nascarnation
As a guy who designed cooling systems 40 yrs ago, I'd say losing 36 degrees F on the boil point is a really big issue.
Add a lot more pressure to the system to compensate?
 
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Originally Posted by nascarnation
As a guy who designed cooling systems 40 yrs ago, I'd say losing 36 degrees F on the boil point is a really big issue.
And losing 8F in freeze protection in Canada, a big deal.
 
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Originally Posted by Chris142
Originally Posted by nascarnation
As a guy who designed cooling systems 40 yrs ago, I'd say losing 36 degrees F on the boil point is a really big issue.
Add a lot more pressure to the system to compensate?
Seems like everywhere I go there is at least one car/truck, whatever that reeks of coolant. I would much rather have those vehicles moving rather than broke down because they will all somehow be on the road ahead of me with a gaggle of rubberneckers.
 
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I looked up both Prestone and Sierra LowTox coolants that are propylene glycol In both cases, the 50/50 freezing point is -26F Prestone's boiling point is listed as 259F Sierra's boiling point is listed as 256F
 
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I don't think you mean polyethylene glycol, instead you mean propylene glycol. One thing is that ethylene glycol doesn't have a very long environmental residence time, it breaks down in soil rather quickly so it isn't quite the boogie monster you may think it is. Yes it is highly toxic to canines but less so to humans. One of the biggest reasons it is used is probably the ease of synthesis as compared to propylene glycol.
 
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Originally Posted by motor_oil_madman
Does the regular green coolant have the embittering agent in it too?
It's not "embittering" it is just bittering. And yes all ethylene glycol coolants have a bittering agent.
 
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Originally Posted by kschachn
I don't think you mean polyethylene glycol, instead you mean propylene glycol. One thing is that ethylene glycol doesn't have a very long environmental residence time, it breaks down in soil rather quickly so it isn't quite the boogie monster you may think it is. Yes it is highly toxic to canines but less so to humans.
Yep.. Humans can ingest it in small quantities before it kills them. Especially if you put it in soup. Watch your soup gents!
 
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I brought up this topic with a trusted mechanic some years ago when I had Sierra coolant in my 89 Accord. He explained to me that once the coolant has spent 30,000+ miles inside your engine it picks up more than enough combustion byproducts to be plenty toxic. My city water treatment people once told me it's actually OK to dump used coolant into one of your home drains or down the toilet because the water treatment process will degrade and remove it.
 

RamFan

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Originally Posted by nascarnation
As a guy who designed cooling systems 40 yrs ago, I'd say losing 36 degrees F on the boil point is a really big issue.
Is is though? Considering you could up the ratio to 55/45 or 60/40 and boost that number. Heck, the FL22 that comes in my CX-5 is already 55/45.
Originally Posted by ctechbob
I was under the impression from an article I read ages ago that there is bacteria in the soil that does a fairly handy job 'eating' up most kinds of coolant types these days.
You know, I think you're right. I too vaguely remember reading this in years past.
Originally Posted by Danno
And losing 8F in freeze protection in Canada, a big deal.
Again, when you can simply change the ratio, is it really that detrimental?
Originally Posted by DBMaster
I brought up this topic with a trusted mechanic some years ago when I had Sierra coolant in my 89 Accord. He explained to me that once the coolant has spent 30,000+ miles inside your engine it picks up more than enough combustion byproducts to be plenty toxic.
Interesting point, I hadn't considered that.
Originally Posted by kschachn
I don't think you mean polyethylene glycol, instead you mean propylene glycol.
Oh jeeze, you're right. crackmeup Thanks for all the responses!
 
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Originally Posted by DBMaster
I brought up this topic with a trusted mechanic some years ago when I had Sierra coolant in my 89 Accord. He explained to me that once the coolant has spent 30,000+ miles inside your engine it picks up more than enough combustion byproducts to be plenty toxic. My city water treatment people once told me it's actually OK to dump used coolant into one of your home drains or down the toilet because the water treatment process will degrade and remove it.
Interesting, where is the coolant coming into contact with the products of combustion? Unless there is a head gasket leak (or a crack in the block) where does this happen? And yes, most municipal sewer systems permit the disposal of glycols into their systems. It is not an issue with the treatment process. Here in southeastern Wisconsin the Milwaukee Metropolitan Sewerage District allows disposal into the sanitary system but encourages recycling instead. However it must never be disposed of into the storm drains nor into a private septic system. That's one of the reasons why when there is an accident involving a coolant spill it is contained and properly disposed.
 
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Originally Posted by kschachn
Originally Posted by DBMaster
I brought up this topic with a trusted mechanic some years ago when I had Sierra coolant in my 89 Accord. He explained to me that once the coolant has spent 30,000+ miles inside your engine it picks up more than enough combustion byproducts to be plenty toxic. My city water treatment people once told me it's actually OK to dump used coolant into one of your home drains or down the toilet because the water treatment process will degrade and remove it.
Interesting, where is the coolant coming into contact with the products of combustion? Unless there is a head gasket leak (or a crack in the block) where does this happen? And yes, most municipal sewer systems permit the disposal of glycols into their systems. It is not an issue with the treatment process. Here in southeastern Wisconsin the Milwaukee Metropolitan Sewerage District allows disposal into the sanitary system but encourages recycling instead. However it must never be disposed of into the storm drains nor into a private septic system. That's one of the reasons why when there is an accident involving a coolant spill it is contained and properly disposed.
kschachn, I wondered the same thing, but didn't ask. If the coolant comes out looking dirty it must have something in it besides just the propylene glycol. There are various additives in coolant and I'm sure it picks up traces of various metals, gasket materials, and lubricants (maybe from the water pump) during its life inside the engine. I wouldn't want animals drinking it regardless.
 
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Indiana
Originally Posted by Chris142
Originally Posted by nascarnation
As a guy who designed cooling systems 40 yrs ago, I'd say losing 36 degrees F on the boil point is a really big issue.
Add a lot more pressure to the system to compensate?
That raises the challenge of building heat exchangers to reliably hold that pressure over a period of many years Certainly possible, but more added cost.
 
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USA
To put it simply, propylene glycol simply isn't as good of a coolant as ethylene glycol is. It doesn't transfer heat as well (which is the whole point of coolant), it doesn't provide as much freeze protection when used in the same concentration, it is thicker, and it doesn't raise the boiling point of the coolant as much. All these factors combined would mean that the cooling system would need a more powerful water pump, larger hoses, and a larger radiator to maintain the same level of performance as with ethylene glycol. This would increase cost, weight, and drag. Propylene glycol is also more flammable than ethylene glycol.
 
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Originally Posted by RamFan
Originally Posted by nascarnation
As a guy who designed cooling systems 40 yrs ago, I'd say losing 36 degrees F on the boil point is a really big issue.
Is is though? Considering you could up the ratio to 55/45 or 60/40 and boost that number. Heck, the FL22 that comes in my CX-5 is already 55/45.
60:40 is pretty darn close to the eutectic point of propylene glycol:water. IIRC from long ago in grad school when I was filling cold fingers with the stuff, 58:42 is the actually point but I called 60:40 close enough and also didn't trust my lab mates to even properly mix 60:40 smile
 
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