The trouble with oiling ceramics is that the surface porosity is much lower than clays. So it isn't very effective, nor does it last for any meaningful amount of time.
I tried car wax once, and while it brought out the colors a bit- it also made the chip
much slicker...
I'm glad I only did a couple, as it took a long time to strip the wax off without messing up the surface. An exercise I care not to repeat, nor can I recommend.
