Coolant - ready-mixed or mix your own?

[benoliver999]

I bought some ready-mix screenwash. There was too much anti-freeze in it and it gunked up the lines. I suspect it might have been the reason my washer pump gave up the ghost.

When it got taken apart you could see the blue stuff clogging it up like my arteries after a full english.

[notsofast]

Well, having said I'd mix my own, I ended up buying ready-mixed when I went to Halfords recently, as the price difference would be negligible, and they didn't have distilled water, only de-ionised.  I've used de-ionised in the past to top-up but then read on some chemicals website that it can acidify over time and cause corrosion, so isn't the best choice (though it's easier to get hold of than distilled).