A face oil does not hydrate. That sounds like a criticism and it is not — it is the whole point. Oils are occlusive and emollient: they slow the water leaving your skin and they make the surface feel smooth. Water has to come from somewhere else, which is why an oil works best over a damp face or over a humectant serum, and does very little on its own over dry skin.
Last, or nearly last. An oil will pass through, but nothing water-based passes through an oil, so anything you apply after it is largely wasted. Serum, then cream, then oil — or serum, then oil, if you are not using a cream.
Two or three drops is a full face. If an oil feels greasy an hour later, you used too much rather than chose the wrong one.
