Umm... what do you do with old coolant?

[Driftwood]

So we've got a cnc mill and a cnc lathe in our shop and we've been around for a few years, but haven't needed to change out our coolant until now... in both machines, it was getting a little oily, particularly on our lathe where all the lube oil for the ways drains into the coolant tray... yuk...

Neither machine has an oil skimmer, so that was our biggest reason for replacing the coolant, but theres no odor or anything... we don't measure the concentration of coolant to water (though we plan to in the future) but we're confident we're on the conservative end...

Anyway... we've drained the coolants into drums, and now we're trying to decide what to do with them... we've let them settle for a couple of weeks, have skimmed off the oils from the top, and assume any solids have settled out...

So then, is this coolant good to go back on the machines? If not, what do you do with it?

Thanks...