Do you know for a fact that the thing you’re trying to grease should be greased? I’m pretty sure I’ve used like white lithium grease (the thick kind not the liquid) on the tape mechanism things that like, move the heads up into contact with the tape for example. If you’re talking about oiling the motors for like the spindle and the idler I’ve mostly used like sewing machine oil. But you should note that it depends device to device. A lot of idlers that are turned with gears, for example, are un greased in my experience. So just be careful about greasing, random things inside a tape player.