NO OIL! not necessary. No, no, no.
That's a question I asked my Pfaff dealer (if it ever needed oil). Definitely a NO. Your CV5.5 is all digital. Now, the needle is another thing... I have a Creative 2170, almost 3 yo. It sounds a bit "thunky", but I'd been away from it awhile and maybe I didn't remember it. I changed the needle, no change in the "thunkiness". (It's overdue for it's maintenance.) I was also sewing thru 7-8 layers of fabric, etc. Get it checked, it's free and better to find out now.