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!