OIL AS A SUNSCREEN
Oils are able to reflect sunrays, but we should not rely on them.
1) Oils have a very low SPF. Additionally, it may differ not only among various oils, but also in one specific oil. For example, SPF of coconut and olive oils could be SPF 2 as well as SPF 8.
In any case, I think you can guess that even SPF 8 could not be considered a decent sunblock. And here are the approximately SPF of various oils:
* shea butter SPF 3-6;
* jojoba SPF 4;
* almond SPF 5;
* sesame oil SPF 5;
* macadamia SPF 6.
2) Oils attract Sun- you will be surrounded by many more sunrays than you would having no protection at all. Your skin guards will be forced to work very hard. Most likely they will lose. You will get a sunburn. Skin will peel. Pigmentation will appear.