It's summer so water would do it. I assume it's an older model as you mention age.
2010 - so not ancient by any means, but still 6 yo. What is the importance of its age?
I was thinking of using either regular pre-mix coolant from halfords or distilled / deionised water with a bit of antifreeze.
@hugo7 started
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It's summer so water would do it. I assume it's an older model as you mention age.