No, you don't oil them. The only maintenance you can do is to keep the bobbin area clean of debris when you finish a project. If I'm sewing fleece or flannel, I clean the bobbin area 2 or 3 times while I'm working on the project, depending on the size of the project.
These little machines are computerized and have sensors that can really be missed up by the layman. I don't take my machines in to be serviced unless, like you, I hear a funny sound or something just isn't working right no matter what I do to try and correct it.