Best Ethylene Glycol/Water Ratio to avoid overheating? Why? Informal Survey.

[Patrick67BJ8]

I used to use the 50/50 ratio as I was told to and I read about it in mag articles. I purchased a gallon of 50/50 for my 2015 GMC pickup and I found out that antifreeze/coolant has changed a lot. The house behind the counter looked up my truck to see which brand/formulation I needed.

Because the Healey is old technology, what is everyone using today?
Brand and strength?

 

[bdcvg]

I am 50/50 pre-mix from Advance Auto

 

[Bob_Spidell]

Nothing wrong with 50/50, but you pay a bit more for it than you would if you bought straight antifreeze and distilled water and mixed your own. Many automakers have their own blend of AF, which I believe is somewhat legit but also serves to pad their bottom lines. They are usually color-coded: old school ethylene glycol blend is fluorescent green, I believe some GM and foreign makes use a red or purple colored type, and my '08 Mustang specifies a gold (yellow) colored Motorcraft or equivalent. Green Prestone or equivalent, labeled 'Suitable for All Engine Types' is appropriate for our iron lumps. It's not advisable to go against manufacturers recommendations and certainly not to mix types; I've heard of coolant gelling when some types are mixed. Some AF blends, specifically those for sale in Canada, require a bittering agent to repel animals, like dogs, who otherwise will lap up a coolant spill like it's melted ice cream, and die a painful death.

Last I checked, the green stuff--Prestone, Xerex, or other--can be had for about $11/gal on sale, and a gallon of distilled water costs about $1. That's $6 give-or-take for one gallon of a 50/50 coolant mix; the premix appears to run a couple bucks more (but the convenience may be worth it). My BJ8 specs 2.5gal (US) for a 'dry' fill, but I've never gotten more than a gallon and a quart or so. I dump a gallon of AF in, then add distilled water until it's about 2" below the bottom of the radiator filler neck; any more than that goes out the overflow pipe.

 

[Joe A]

Sensible post, Bob . . .

On a new or newish vehicle, I'd follow the manufacturer's recommendation without hesitation.

I was reflecting on my dialog with the other "Joe" and what came to mind is that we were having the discussion in a context as if the cooling system was going to contain 100% water. I'd never use 100% deionized water and I doubt that anyone here would dream of doing so. 50% distilled water? I still don't see a problem. We did not touch on the probability that distilled water may interact with the anti-freeze in such a way as to render any concerns moot.

I think the underlying concern in choosing distilled water over tap water is the potential for mineral content in "hard water" causing problems in the long run. It's the demineralization people are after.

In my case, the tap water available to me is relatively soft.

I have an inexpensive (under $25) Sunny brand Chinese TDS&EC electronic tester purchased through Amazon and the particulates in my tap water are in the range of 60 to 80 PPM. So, no problem blending tap water with "the green stuff."

When I replaced my radiator recently and flushed the block, I was pleasantly surprised that what came out of the engine was free of any observable particles.

Edit, aside for the curious among us: I bought the TDS&EC tester, not for the Healey, but because we had a well dug to use for irrigation water. Some plants were doing OK while others were dying. We live near a canal. Turns out that, while our well-driller told us the well water was suitable, it tested as 1500 to 1800 PPM of particulates which, in our case meant we were watering our garden with brackish water. Good thing I did not use that water for the Healey!

 

[why]

Never ever ask a fluid replacement cycle question, in particular brake and coolant. They come out of the woodwork.
Jay, '65 3000 MK III

 

[John Turney]

This is sort of an odd thread because I am actually most interested in where/how you learned the answer to the following question:

What is the best ratio of ethylene glycol to water in coolant for a car which has overheating issues (and freeze protection and rust protection are not a concern).

In my forum reading here and elsewhere, the common answer is that less ethylene glycol is better because the specific heat of water is higher than EG. But I have read some older Society of Automotive Engineers papers which contradict this common wisdom. They say more EG makes a car less likely to overheat (up to 70%). So I am confused right now.

So ignoring all other issues (freeze protection, rust protection, water pump lubrication, etc.):

1) To avoid overheating, is less ethylene glycol better?
2) Where/How did you learn this (1st hand experience? the internet? engine handbooks, etc.)?

....

Both of those things you learned (water is a better heat transfer fluid than ethylene glycol (EG), and adding EG to the water raises the boiling point) are true, and not mutually exclusive.

• At 0.0 psig (14.7 psia), water boils at 212 deg-F; at 7.0 psig (the relief point of your radiator cap, water boils at 230 deg-F. If coolant temperature doesn't exceed 230 deg-F, water alone is better. https://durathermfluids.com/pdf/techpapers/pressure-boiling-point.pdf
• At 7.0 psig, water with 50% EG boils at 245 deg-F.
• At 7.0 psig, water with 60% EG boils at 250 deg-F.
• At 7.0 psig, 100% EG boils at 345 deg-F, but the heat transfer is much worse than with water or water/EG mixture, so you are more likely to hit 345 deg-F and ruin the engine.

Of course, even if you went with 100% water, you still need corrosion protection and water pump lubrication, so the 50/50 mix is a good compromise. Boiling much higher than 230 deg-F would take your temperature gauge off scale so you wouldn't know what your temperature is and likely lead to engine damage.

 

[shortsguy1]

Hi Everyone. Thanks for all the great replies to my questions. I appreciate it very much. Have a happy Thanksgiving (or a happy Thursday, depending where you live).

 

[Healey Nut]

Speaking from my HVAC background where I deal with glycol systems a lot .
water has a higher latent heat capacity than water , as soon as you add glycol to it it lowers its ability to transfer heat .
Now as we know we need corrosion and lubrication properties for the system
Therefore adding only enough glycol to provide protection to whatever your lowest ambient temperature is is the way to go but do not go more than 50/50 .
On a separate note glycol doesnt actually freeze like water and has a lower expansion rate than water . It turns to a jelly like substance at its freeze point .