The purpose of oil is to condition your hair contrary, to what is commonly believed, oil does not aid hair growth nor does it nourish it. However, an oil massage is soothing and relaxing, and stimulates circulation is the scalp to some extent.
For its conditioning effect, oiling your hair once a week even for 1-2 hour is enough.
By and large, any oil is as good as the other. However, it is better to avoid oils with perfume and color.
If you have and oily scalp, do avoid oil. Sometimes oiling can increase Dandruff. You need to keep this is mind by using any oil on your scalp.
Apart from the hair oils available commercially, you can also use edible oils like sunflower, olive, safflower, groundnut, etc. Sometimes, these help additionally for dry scalp.