Coolant purchased from VAG dealers I presume is already mixed and just pour into expansion tank. On previous cars I have owned I have topped up with ionised water (distilled water) as it does not drop scale or limescale into the radiator or engine when hot. Interesting is the already mixed coolant ionised water or local tap water.

Edited 21 January, 201610 yr by edbostan

Just to be pedantic distilled and deionized water aren’t the same, I would only use distilled as deionized water as it’s said to be more reactive to metal.

Not sure how VAG supplies their coolant, it looks to be of the OAT type that is available from most motor factors both ready mixed and neat. I wouldn't be surprised that in the VAG factories that normal local tap water is used unless it is in a very hard water area OAT can suspend some minerals in the water stopping them from forming any scale

Edited 22 January, 201610 yr by ChrisTids

Thanks for that tip. I will only use distilled water as I thought they were the same animal

Vag coolant is not ready mixed. Euro Car Parts do sell their own brand G13 coolant, either neat or ready mixed.

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As above, genuine vag stuff comes neat normally, on the label it tells you the dilution ratio you need to do for certain temperature protection ranges.