Most, but not all Gits oilers are pressed in, not screwed in. However, some are screwed in. You should be able to tell by looking carefully at the oiler where it goes into the casting. The press in oilers are often not removable without destroying them. Installing them can also destroy them. I use an accurate fitting wood dowel installed into the opening with the lid held open and out of the way and then drive them in. 90 degree versions need a U shaped driver that fits the contour of the oiler if rounded opposite the neck, or a flat one if flat. The screw in ones need to be unscrewed to remove. Try to save and reuse them, they are getting more expensive and lower quality with time, IMO. A lot of sizes and styles have been discontinued with no similar replacements currently available new.