Just having a nose through the manual and it says 50/50 mix of coolant and distilled water, question is why the distilled water?. Does it make a difference or is it for the protection of the water ways internally?

Only looking at it now because its got cold...

Richy

Distilled water has got the calcium removed, so it stops the limescale/calcium deposits building up inside the rad and its associated pipes. This prevents the pipes becoming furred up/blocked and working less efficiently.

Or you could just buy Silkolene Pro Cool, which comes pre mixed, so you can just pour it in!