It’s probably not your oiler that’s limiting the oil getting to your bar, I’d bet it’s the oil port on the bar. Stihl’s ES and the newer Oregon bars have a tiny little oil port and if your oil has any viscosity at all it’s game over.
Carbide anything works great in a mill or a drill press where nothing can move. If it chatters... Game over. You need a diamond wheel to get them sharp too. A good HSS bit will drill it with some decent lube-HP Ultra works great in a pinch, Red Armor and Saber aren’t as good.
Source: Bucket of broken end mills, lathe inserts and drills in the machine part of my shop.