i try to limit the amount of water i put anywhere near my steel based router system. whenever i'm too forgetful to drain the air compressors and end up putting wet air through the mister, all my chucks get a nice glaze of rust. Always game to try something new, however, as oil prices are skyrocketing. (Thanks O'Biden)
i currently use TriCool MD7 vegetable-based oil/coolant. The TC1 synthetic is good too, but it has always been the culprit of the oil-pooling (that I referenced above) as it runs so thin that it flows like water even on the lowest oil output setting.