Paul - I'm struggling to consider 1 litre of fluid over an 8 hour period to be a "coolant", rather than a lubricant. That's around 2ml per minute if my sums are right. Even if it were fully evaporated during machining, that's got to be a fairly small cooling effect. When you say it works incredibly well, are you referring to the surface finish rather than the temperature of the cutter and work?