I'm not completely sure about the 401 or model 15, but more modern swing arm zigzaggers usually doesn't have felt wicks like the old straight stitchers have. My 66, 99 and 201 only have a felt bit in the top of the presser bar tension screw. None of my more modern machines has oil wicks at all (late 50s and up). The 99 has a red felt bit near the hook and race too. There's usually a lot of hinges and oil points connected to the movements of the needle bar though. The most important thing is to make sure there is oil in the hinges as well as all the way along needle / presser bar shafts.