I've only every milled aluminium with a spray mist/coolant/lubricant.
Yesterday I used a machine that didn't have this and so splashed oil on everything with a paintbrush.
Afterwards noticed that there was a lot of rotary scratching on the faces of the material.
Was that because there was no spray mist?
Or was it for some other reason (it's true the mill had a max rpm of only 3000 but slowed the feed accordingly as per Gwizard).