The G12 coolant specifies it should be mixed with TAP water. Ordinary drinking water. It's cut and dry.

And yes it is a bad idea to run anything other than G12. No aftermarket company produces a coolant that meets Audi's specifications, and the ones that say they can be used with all cars are lying.

 

I'm just saying what my service guy at the Audi dealership told me to do. TAP water, especially where I live, can contain a lot of unknown contaminants. I've been told by a plumber in my area that living in the area of the Twin Cities where I live (west side) having a water softener is almost required because the water is so hard it will eat the pipes out of your house.

For 99¢ I think I'd take my chances with a distilled water, but you are right - it shouldn't be required.

 

some companies make coolant equiv. to G12, and this G12 stuff isn't all that our cars take. its an oem type of thing, and of course the dealership will tell you to stick to oem, keeps business. i went down to my local pep boys and there is aftermarket coolant compatible with our cars, don't be silly.

 

Yes its compatible if you first flush the oem coolant out of the system, completely. Mix the G 012 A8FA4 with an aftermarket G-12 and prepare for problems. Trust me nothing is compatible to mix with our G-12 other than OEM Audi/VW coolant(Pentosin produces it). Barefootpanda was asking about topping off. Not doing a cooling system Flush.

Barefootpanda, if you have mixed the OEM G12 coolant with other than Pentosin or the OEM G12, you need to flush it and go one or the other. I'd stick with the OEM G12. I really can't believe people will nit-pick over paying $10 more for OEM fluids and not think twice about spending whimsically on non-essentials. Proper maintenance is no#1 in my book. I'd bet our cars would all have a higher resale value if more of us put emphasis on maintenance first, mods second. And I do agree to use a distilled water if the mineral content out of the tap is high.

Heres from another forum:
VWTech8176
Member posted 05-12-2005 07:53 AM
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IF you think there is a storeage of distilled water in VW dealerships for topping off batteries and diluting coolant, you're absolutely nuts. The coolant in our shop gets diluted with tap water just like any other coolant.

Up-The-River
Member posted 05-11-2005 10:17 AM
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You might want to call VW Customer Care or their tech line before mixing G12 with Dexcool.
I wouldn't recommend mixing the two fluids. You can flush (& reflush) with water, then replace the G12 with Dexcool, if you feel the need, but mixing the two is not the best thing to do. (FYI mixing in some green antifreeze will turn the fluid into an orange goo of death.)

Just use the right G12 fluid & eliminate one more chance of something going wrong.

 

Yeah krystallbluea4 is right, all shops use tap water to mix the coolant. However! distilled water is perfectly fine, and technically better (but seriously... the mineral content is negligible).

I don't know how many clogged heater cores and cooling systems I've flushed out due to people mixing any other kind of coolant with the G12.

 

I had a similar situation as BareFoot. I started my car Monday morning....car went beep "low coolant" . So I popped the hood, and my coolant level was very very low. I keep a bottle of 50/50 prestone in the trunk. Its just what I have, and I had it from my last car so I just transferred it over. That was monday and car is still running great. No heating problems, or lack there of. Honestly, not being a huge mechanical genius, it doesnt make sense for prestone to say" works for every make, every model" when apparently according to some folks it should say "works on all makes except Audi". I would think they are walking into a death trap of law suits if in fact there product is not safe in all makes and models. Just throwing that out there. Now that I said this, watch the car blow up tomorrow.

 

Now that "all makes all models" MAY be compatible but still not advised. There are lots of situations where things apply to all vehicles BUT Audi. When you mix the coolant it's not like an explosive reaction. It slowly sludges up over time, just accumulating on the surfaces of the cooling system.

 

WOW!! A whole three days! Good luck with your car! What were you expecting? A violent chemical reaction? Before you rest too easily, check the list on your bottle of coolant to see if its compatible with your car/G12...I'll save you the time, it's not. You see, it's not the liability of the aftermarket coolant manufacturer, its yours. You could check out your owners manual if you want to see for yourself...its page #284. I'm pretty sure the factory repair manual specifies not to do it as well. There's a ton of info out there if you search for it.

Ultimately, do what you want, it's your car.

 

G12 and distilled here since day one. Drained system right after I bought car (new) to do some work in service position. Drained system recently since I'm pulling block to do a 2.0 stroker, and the coolant looks brand new. Lines all spotless. Almost 5 years in.
That is worth the extra couple of bucks to me. Get the G12 at VW dealers, though. Usually cheaper.

 

I added Preston 50/50 to a 2001 A4 and nothing happened after a year and a half. I've put 15000 miles on it since then, no problems.