Ideal water-to-antifreeze ratio

I understand that water is a better coolant than antifreeze. Therefore if cooling were the only consideration, we'd run with pure water. However, we need protection against freezing and the water pump lubrication provided by antifreeze. So my question is, if we're not that worried about freezing, such as in the mild climate where I live and where my cars are not left outside overnight anyway, what's the minimal percentage of antifreeze in the coolant to provide adequate water pump lubrication?

I know that the default answer to the question of the best water-to-antifreeze ratio is 1:1 (50/50), but here in a mild climate that seems like overkill for freezing protection and accepting a loss in cooling capacity by reducing the ratio of water when it could be, say, 20 percent antifreeze and 80 percent water.

Your thoughts?

When I drain the radiator and block, I put in a gallon of antifreeze, then top it up with distilled water (about a gallon and a quarter give-or-take). This has worked in all climates for many years and miles.

I do as Bob and fill with one gallon of antifreeze and top of with water. However, I have a well that requires a softener to address the iron content of the water. Even using water that requires softening, I see no indication of any sediment in the radiator, recovery bottle, or in the drained antifreeze and take that as an indicator the antifreeze’s anti-corrosion additives are working. Or, am I being optimistic?

Ray (64BJ8P1)

I live in sunny southern California and was told by an engineer at Royal Purple that 20% antifreeze is adequate.

I'm using a 2:1 water to coolant ratio. When I put the car up for winter I'll go to 50:50. If I was looking for maximum cooling, I'd run distilled water with one of the water wetter type additives that provide corrosion protection and water pump lube.

HealeyRick said:

I'm using a 2:1 water to coolant ratio. When I put the car up for winter I'll go to 50:50. If I was looking for maximum cooling, I'd run distilled water with one of the water wetter type additives that provide corrosion protection and water pump lube.

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I did this for a couple of years and enough rust was created to partially clog my radiator and cause overheating. Whereas before and after I was running coolant and never had a corrosion problem.

There is a lot of discussion on WW in online forums. My takeaway is it is an obsolete product and has been superseded by newer products, such as those by Royal Purple.

I've been running the Tefba cooling system filter for two years with the 20% coolant mixture with absolutely no rust bits showing up in the filter.

The RP engineer also said tap water is better than distilled water as the minerals in it actually attract the rust ions (think I got that ion part right).

steveg said:

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The RP engineer also said tap water is better than distilled water as the minerals in it actually attract the rust ions (think I got that ion part right).

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I only have an Associate's degree in chemistry, but there's no principle of chemistry that supports this idea that I know of. I've heard variations on this before; usually something like distilled water is 'ion hungry.' Distilled water will dissolve more of a polar compound--e.g. salt--because it's further from saturation than tap water (if you have salt in your cooling system well, you got other problems). Got any chemists on the Forum?

I believe most car manufacturers recommend distilled water. From my 2008 Mustang's shop manual: 'Recommended coolant concentration is 50/50 ethylene glycol to distilled water.' They also recommend 40/60 antifreeze/coolant for warmer climates (60/40 in cooler climates).

I wish I had read this yesterday before I filled up with 50% + Royal Purple "liquid ice" additive.
Seems that in Vancouver a lower antifreeze concentration + the additive would have been better. I too would like to know what is the ideal lower concentration with and without the additive

Me TOO:

One gal coolant then top up with water.

Manufactures recommending distilled water are simply trying to prevent the car owner from experiencing the effects of "Hard Water".
Could be a liability issue too?

The principle behind WW and, presumably, the RP product, is to introduce a substance--called a 'surfactant,' short for 'surface active agent,' or 'wetter' (soap is a surfactant)--that reduces the surface tension of water (surface tension creates the meniscus and allows water bugs to skit across the surface; my father would add a surfactant to the mixture when he sprayed trees to help the mixture spread evenly on leaves). In theory, at least, this allows the coolant to spread more evenly on the engine surfaces allowing more heat transfer and to reduce (or prevent) localized boiling and reduction of overall cooling capacity. WW also adds a lubricant for the water pump seal and an agent, I believe oxalic acid or similar, to maintain the correct coolant pH to either a) minimize corrosion, b) neutralize high-pH substances created as antifreeze ages or c) both of the above (the reason you change out coolant occasionally is because the neutralizing effect diminishes over time and, possibly, to remove sediment; water and glycol would last longer than your car). This means you can use WW (or RP) without antifreeze for maximum heat transfer to the atmosphere. I've used WW with antifreeze/water in the past, but didn't see any meaningful reduction in running temps.

Healey 6-cyls--at least, the 2,912cc sixes--have about 2.5 gals of coolant capacity. Assuming you drain the block--there will likely be some old coolant left in lower areas--adding a gal of antifreeze and topping off with your favorite water would be fine for all but the coldest climate.

RAC68 said:

I do as Bob and fill with one gallon of antifreeze and top of with water. However, I have a well that requires a softener to address the iron content of the water. Even using water that requires softening, I see no indication of any sediment in the radiator, recovery bottle, or in the drained antifreeze and take that as an indicator the antifreeze’s anti-corrosion additives are working. Or, am I being optimistic?

Ray (64BJ8P1)

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Nope. If you don't see any sediment when you drain the coolant you're fine (although some sediment can get trapped in lower areas of the cooling system).

Yes, distilled water is recommended to prevent dissolved salts--usually carbonates, in particular calcium carbonate--present in most tap water from being deposited on surfaces ('hard water' just has higher concentrations of calcium carbonate). These deposits--sometimes called 'boiler scale'--WILL reduce the cooling system's efficiency, and when it flakes off you get sediment. I don't believe distilled water--some say demineralized is even better--has any inherent advantages other than to prevent scale from forming.

Unfortunately, the concentration of antifreeze in our coolant is a bit of a compromise (even if you ignore boiling/freezing temperatures). Higher concentrations (40-60% antifreeze) will enable you to go a couple of years between changing out your coolant. That is one of the main reasons why these concentrations are recommended even for mild temperature climates. If you run less than 40%, I would simply recommend that you change your coolant out more frequently. I decided to run 30% in a mild climate in CA. The car had not seen a coolant change in a long time and has a lot of internal rust. I didn't want to go lower than that for corrosion reasons, even though the climate would have allowed it. I plan to change out the coolant in 1 year and see how things look internally at that time.

shortsguy1 said:

Unfortunately, the concentration of antifreeze in our coolant is a bit of a compromise (even if you ignore boiling/freezing temperatures). Higher concentrations (40-60% antifreeze) will enable you to go a couple of years between changing out your coolant. That is one of the main reasons why these concentrations are recommended even for mild temperature climates. If you run less than 40%, I would simply recommend that you change your coolant out more frequently. I decided to run 30% in a mild climate in CA. The car had not seen a coolant change in a long time and has a lot of internal rust. I didn't want to go lower than that for corrosion reasons, even though the climate would have allowed it. I plan to change out the coolant in 1 year and see how things look internally at that time.

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Why not do a cooling system flush to get rid of (some of) the existing corrosion and, possibly, scale?

I race mine as well as driving on the street - to and from the track and normal driving. We are not supposed to run antifreeze on the track because of how slippery it is and the difficulty of cleaning up if there is an accident. So for over 15 years I have not had antifreeze in mine except occasionally in a few winter months.
I run tap water and water pump lube only and never have sediments and no cooling problems (other than our typical problems with too much idling/slow speeds in heavy stop & go traffic). So, in my opinion if you are not worried about freezing, there is no reason for antifreeze as long as you have a lube/anti rust for the water pump seals. BTW I tried water wetter years ago but never found any noticeable improvement in cooling.

red57 said:

I race mine as well as driving on the street - to and from the track and normal driving. We are not supposed to run antifreeze on the track because of how slippery it is and the difficulty of cleaning up if there is an accident. So for over 15 years I have not had antifreeze in mine except occasionally in a few winter months.
I run tap water and water pump lube only and never have sediments and no cooling problems (other than our typical problems with too much idling/slow speeds in heavy stop & go traffic). So, in my opinion if you are not worried about freezing, there is no reason for antifreeze as long as you have a lube/anti rust for the water pump seals. BTW I tried water wetter years ago but never found any noticeable improvement in cooling.

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What brand of water pump lube are you running and how often do you change the mixture out?

My problem might have been that I expected the WaterWetter to do the lube etc job and it wasn't up to the task. My radiator guy said one could use water-soluble oil mixed with water but all this adds up to more hassle and uncertainty than just using coolant and water.

I consulted my notes and what the Royal Purple guy said was to use purified drinking water from the supermarket which would have a very slightly higher pH than distilled.

Here's a good video about coolant testing including testing the voltage with a multi-meter:
https://youtu.be/mHTM3dvpD1M
He says it should be .3v (300mv) or less with a pH of 8.5 - 10

Steve, I really don't know the pump brand - it's at least 10 years old and probably came form Moss. I don't have a preset schedule for changing/flushing but because things get reworked regularly for various reasons (if you like tearing things apart and putting them back together regularly, racing is for you), I'm guessing it probably has gotten changed at least every couple of years, and sometimes much sooner than that. In fact, that's another plus about not running antifreeze - no disposal issues.
Dave

Bob_Spidell said:

Why not do a cooling system flush to get rid of (some of) the existing corrosion and, possibly, scale?

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Is there an accepted methodology to internally clean these cooling systems? I am most familiar with old Mercedes diesels, and MB recommends a citric acid flush which I have used with success. But BMC said to not use any chemicals to clean the cooling system (I forget their exact wording), so I was hesitant.

Have any of you had success with any specific flush methodolgy?

There are several products for flushing radiators (Prestone has at least two with, I believe, different strength). Usually, you pour it in and run the engine for a while. There are also kits to back-flush the system; but I've not used them. Probably a good idea to remove the thermostat. The 'trick,' is to make sure you get all the flush out; which entails either back-flushing or running lots of fresh water through before re-filling with water and antifreeze.

Bob_Spidell said:

There are several products for flushing radiators (Prestone has at least two with, I believe, different strength). Usually, you pour it in and run the engine for a while. There are also kits to back-flush the system; but I've not used them. Probably a good idea to remove the thermostat. The 'trick,' is to make sure you get all the flush out; which entails either back-flushing or running lots of fresh water through before re-filling with water and antifreeze.

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When I change the old coolent out (which I just did yesterday afternoon), I back-flush the system first. I use the Prestone kit and Prestone flush.

Drain all the old antifreeze out.
Unclamp the heater hose from the block, clamp a new short hose in it's place, install the Prestone t-section between the two hoses and connect the garden hose there.
Leave the radiator cap off and plug in the Prestone right angle textention tube in there.
Put heater on high.
Radiator drain plug still open.
Turn the garden hose on. When water is flowing out the top and bottom of radiator, start the car and let it run till water comes out clean.
Turn car off.
Remove hose, put the Prestone seal cap on there.
Drain radiator till it's 1/2" from top. Close the drain plug and pour in a bottle of Prestone flush. Put the radiator cap on.
Run the car 10 minutes till warm. Run the car another 10 minutes.
Turn car off, drain everything.
Put hose back on, radiator plug open, radiator car off, Prestone tube in where the cap was, turn on hose. When water is flowing out both ends of the radiator, start the car. Run till water comes out clean.
Turn off car, remove garden hose, drain all water out.
Remove the t-section from the heater hose, reconnect the heater hose, close Radiator drain plug.
Add one gallon of your choice of antifreeze and one gallon of distilled water.
Leave cap off, start car and run to get all the air out. Check for leaks.
No leaks, take the car out for a ride and check the antifreeze level when home.
Pat yourself on the back, job well done!

My homemade setup - radiator off and thermostat removed:
Combination of 1" pvc union with hose shutoff:

I used the Healey hoses and an old stocking to see what would turn up in the net.