What the difference between the oil you buy in the shop and massage oil?

What the difference between the oil you buy in the shop and massage oil?
My son and his wife are both registered massage therapists and my son teaches courses at a school of massage therapy. They buy grapeseed oil from the supermarket. It's considerably less expensive than the specialized massage oils but really, the only difference is the grapeseed oil is odourless. If you set up a scented candle in the room, it will be all the scent you need. The main purpose is just to ease hands gliding over the skin.
I need to buy massage oil for a course i've just started, and wanted to know what the difference between grapeseed oil bought from a supermarket and massage oil is?

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