First of all, you need to understand skin is an organ. There’s nothing simple about it.
Secondly, oils are very complex too. They are formed by many compounds like vitamins or aminoacids that will interact with your skin. Every oil has a different composition and it will interact with the skin on a molecular level.
Having that said, and to answer your question, the oil will provide the skin what it needs to function. In your case Grapeseed Oil is rich in vitamin E among many other things, which is an antioxidant, and the skin will “use” it.
And since every skin and every oil is unique, the interactions are infinite. And that’s pretty much why there’s this thing called “cosmetic chemistry” and a billion dollar industry that studies the components and the interactions.
Bottom line, don’t play around with your skin and don’t put on anything on it if it hasn’t been approved by a doctor or a cosmetic chemist.