We have always used water for our cooling, but since this is a heat transfer condition, you should be fine with any form of coolant.
We live in a cool part of the USA. My CNC is in an unheated garage and temperature gets to -10 degrees Fahrenheit. So we use 100% anti-freeze that is used for winterizing campers. Use same coolant year round. Put 3 gallons in a bucket with fish-tank pump, and it works great. Since there is 3-gallons of coolant, no need for fans to cool the coolant. Just pump from tank to spindle back to tank. And no worry about frozen coolant.
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Okay guys, what fluid are you using for the spindle to keep them cool? do you recommand anything else beside water for the spindle?