Never run a diamond cutting blade dry as it can immediately damage your blade. Coolant oil should be kept clean and below 100 degrees F.  Sludge should be removed periodically and replaced with fresh coolant oil so your cuts will be clean and your blades will not be damaged. 

This Non-hazmat replacement oil excellent lubricating properties for blades and saw parts.  It flushes sludge from rock easily, degreases easily and sludge settles in the saw tank well.   Comes in a one gallon plastic jug.