Then, I look at fatty acid profiles of oils high in oleic acid I find...
olive oil (78%)
high oleic sunflower oil (74%)
hazelnut oil (66 to 85%)
avocado oil (75 to 80%)
Avocado oil feels soft, spreads long, and seems to absorb at a medium rate. Olive oil seems about the same. Sunflower oil, on the other hand, feels rough and dry. And, hazelnut oil feels a dryness somewhere between avocado and sunflower. Why is that? Is it related to other fatty acids in each oil?
Although I don't think you can judge the nature of an oil by the fatty acid composition alone, I think it will give you some valuable information. For instance, if you see that there are loads of oleic acid and linoleic acid, you can guess that it's probably a more liquid oil than one filled with stearic acid or myristic acid, both of which are solid at room temperature. If you see that the oil has more cis bonds than trans bonds, you can guess that the one with more cis bonds will be more liquid than those with the trans bonds.
Want to know more about cis and trans fats? Check out this post! Curious about how to figure out the melting point of butters? Check out this post!
phytosterols, polyphenols, vitamins, tocopherols, and more. So when you consider something like hazelnut oil, you can consider the fatty acids, but also take a look at the tannins, which will make it feel drier than something like olive oil.
I think you also need to consider personal interpretation for skin feel. For instance, you say you think sunflower feels rough and dry, while I feel it feels very slick and greasy.
As an aside, fatty acids that are not part of a triglyceride are called free fatty acids, and there is some indication free fatty oleic acids might be disruptive to the skin's barrier and increase transepidermal water loss. (Take a look at this post to learn more.) This is one reason to consider the greater picture when looking at the fatty acids of oils.
So, as you can probably tell, I don't think that you can judge an oil by its fatty acid profile alone because there are just too many variables that go into how an oil will feel, what its melting point will be, what it offers to our skin, and so on.
Join me tomorrow as we continue our look at fatty acids!