[duncanb]

When I got my i30 new, I noticed the coolant level was just above L when cold, and only slightly higher when hot. So, because I used to drive an old car which I just topped up with water,  I checked in the handbook as to what needed to go into the coolant reservoir.

I was surprised to find out how complicated it all sounded. The handbook says this:

- When adding coolant, use only deionized water or soft water for your vehicle and never mix with hard water in the coolant filled at the factory. An improper coolant mixture can result in serious malfunction or engine damage.

- The engine in your vehicle has aluminum engine parts and must be protected by an ethylene-glycol-based coolant to prevent corrosion and freezing.

- DO NOT USE alcohol or methanol coolant or mix them with the specified coolant.

I asked the dealer about this and he said it's no problem - just top up with tap water. I'm a bit confused by this and just want to clarify. I'd like to take the best possible care of my "baby", and the handbook sounds pretty serious about "only deionized water" and the "ethylene-glycol-based" coolant.

When I checked the local auto store they had a whole bunch of different waters but they seemed mostly for batteries: distilled water, "battery" water, and others I can't now remember - nothing "deionized" to be found. Can I just use distilled water? What can happen if I use tap water and it happens to be "hard" like the handbook warns?

Help!

[Shambles]

I've never had to top up my lil' Fergie, but if I did I'd use tap water, as I've recently done with our RAV4.

Our tap water is soft BTW. I wouldn't dream of doing the tap stuff if we had hard mineralised water with calcium or magnesium content.

Bumpkin's our chemical weapons expert... I wonder what his thoughts are...

[StarSeeker]

I know where you are coming from with this, I had the same concerns.  When I spoke to a couple of garages, they said that when they replace the coolant in an i30 petrol, they use tap water .  I'll worry about that when the coolant needs changing.

What water I used for topping up was this below, also used in engine cooling systems according to the label.

http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_167192_langId_-1_categoryId_165629

[asathorny]

I once did a little top up, it didn't really need it, I was looking for stuff to do.  Same as Shambles I live in a soft water area.  If I lived in the south of England which is mostly hard water then I probably would worry a bit about it, I used to live down there when I was a young student and their water just furs everything up :-(.

So as Steve says it's over to Bumpers for the difinitive and differential assesment of this situation 

[eye30]

Good old tap water.

Don't forget that once the engine gets to operating temp the new water will mix in with that already there.

[StarSeeker]

Don't forget that once the engine gets to operating temp the new water will mix in with that already there.

It probably will eventually, but it takes ages

[BC]

As everyone agrees, tap water ok unless the water is hard & full of minerals.  Otherwise use the purified water that's available-this is usually used for batteries.

[beerman]

I was always told only top up with tap water. Apparantly if you use coolant and get a different one, the chemicals can go to war, with the collateral damage being your engine.