I didn't use any oil at all. I've tried it in the past with WD40 and also water (not together) but it always gets whipped out the groove so fast! Even if I start out thinking I'll just use a tiny bit, the place gets flooded pretty soon. Yes the cut is much better, but I was under the impression dry milling was entirely possible.

I've ordered the bits to do flood milling. I just need to think about the best way to drain coolant from the bed.

I've also ordered a ripper mill so I bet that will extract chips better and not clog as much.

I got a bottle of this for coolant mixing - G/P Soluble Cutting Oil Coolant White Water 1 x 1 ltr | eBay