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My housemate who works in Holden says to use rain water instead of distilled water to mix with the antifreeze. Though I've read everywhere that distilled water should be used, (I'd personally be on the safe side and just use distilled) but I thought I'd ask your thoughts on this. He says rain water has more 'body'?

I flunked high-school Chemistry so don't really know the molecular difference between demineralised, distilled, heavy-water, etc., but when something is cheap AND have been used for decades AND works, I stick to it.
- 5L Distilled water from supermarket = $3
- 5L Coolant from Supercheap/Autobarn/K-mart = $5-$25

You change the coolant every few years.....

I wouldn't use rainwater. Sure it doesn't have additives/fluoride etc thats in tap water. But it can have dirt, organisms, rust/twigs/concrete/moss or whatever that travels from the roof to the rainwater tank. It's a very old bomb thing to do.

Distilled/demineralised for sure. I use it along with Redline's Water Wetter.

So would I'm getting them tomorrow. But I'm just considering the reasons for using rain water. I understand not to use tap water because it has a lot of heavy minerals (especially here in Adelaide's tap water). But what could rain water have that distilled doesn't to make him argue for rain water?

I'm going to guess he doesn't know what he's talking about. Although, ask him. Might be interesting.

SuperMazdaKart wrote:I'm going to guess he doesn't know what he's talking about. Although, ask him. Might be interesting.

He's been working at Holden's for 10 so years so he's at the very least more knowledgeable than me.

How much of the Water Wetter do you add to your coolant/distilled mixture?

Half of the bottle to a radiator with the rest being water in my Familia GTR. Which happens to also be the general rule of half a bottle for most 4 cylinder cars. The V8s generally use the whole bottle to a radiator. It can work with coolant as well.

Hope your friend isn't a Roger Cordia lol.

But the manual recommend glycol-based antifreeze. Is there a very noticeable difference in temperatures?

Not with the way I drive it. However theres plenty of people who swear by the stuff, it's made by Redline.

Rainwater might be OK in your coolant system .... or it might cause it to corrode. Depends on where you are and what's in the rainwater. Point is that there is no quality control on rainwater and it's not treated in any way. It can contain whatever it picks up in the air and on your roof. Rainwater is more acidic than distilled water because it picks up carbon dioxide from the air, which converts to carbonic acid. Rainwater pH is typically around 5.5 compared to around 6.5 for distilled water. This means it is about ten times more acidic. Even worse, if you're anywhere near heavy industry or a coalfired power station (eg Latrobe Valley, Hunter region), rainwater picks up sulphur dioxide in the air and that forms sulphurous acid, ie acid rain. Some places in China have pH < 3.5 in rainwater! As drinking water, that's no problem. But it's not a great idea to put it in your cars cooling system when you have a very cheap and easy alternative of distilled water.

Ask your Holden friend what they put in the Commodores they make there. Bet you it's not rainwater. Sounds like he's having a laugh. Like asking the new recruit to find a skyhook or a "long wait/weight".

Demineralised is the stuff not distilled

Demineralised water is just a cheaper type of purified water that has similar quality to distilled water. Both are suitable for automotive coolant systems when mixed with antifreeze. We use all sorts of purified water here at work: distilled, deionized, reverse osmosis, Milli-Q, you name it. Further reading:
http://en.wikipedia.org/wiki/Purified_water

GP wrote:Demineralised is the stuff not distilled

from
http://en.wikipedia.org/wiki/Purified_water

Purified water is water from any source that is physically processed to remove impurities. Distilled water and deionized (DI) water have been the most common forms of purified water.

Deionized water = Demineralized water

For many applications, cheaper alternatives such as deionized water are used in place of distilled water.

Distilled or deionized water are commonly used to top up lead acid batteries used in cars and trucks. The presence of foreign ions commonly found in tap water will cause a drastic reduction in an automobile's battery lifespan. (Not a problem if you are using the correct Gel Cell)

Distilled or deionized water is preferable to tap water for use in automotive cooling systems. The minerals and ions typically found in tap water can be corrosive to internal engine components, and can cause a more rapid depletion of the anti-corrosion additives found in most antifreeze formulations. Distilled or deionized water is especially important in automotive hybrid system component cooling systems, mixed with hybrid system coolant, to prevent corrosion and/or electrolysis of hybrid components.

Guran wrote:Demineralised water is just a cheaper type of purified water that has similar quality to distilled water. Both are suitable for automotive coolant systems when mixed with antifreeze. We use all sorts of purified water here at work: distilled, deionized, reverse osmosis, Milli-Q, you name it. Further reading:
http://en.wikipedia.org/wiki/Purified_water

Damn you Guran, beat me to it by a distilled second

I know what it is, Just saying that demineralised is better in my opinion. Distilled is not necessary