Today someone who works with CNC machines told me that Cutting Oil takes away more heat as compared to water thanks to some chemicals added specifically for this job.
Regarding flow, he said that it would not be a noticeable difference. And that I can increase the water ratio for better flow.
Nevertheless, I will check it out practically myself.
Also, the merchant told me that cutting oil is made from some chemicals added to diesel. Oil thus, is diesel oil.
Excellent link btw.