Putting oil in your hair just makes one over-shampoo in the struggle to wash it out thereby drying it out more.
Do you colour your hair? Dying hair can also make your hair very dry.
Kerastase mask is probably the best thing out there right now. During shower after shampoo, put it on and leave in for 5 min. If you steam it, it absorbs better and of course the longer you leave it the better it is. Not to mention it makes your hair smell super nice. It’s 60+ but lasts quite a few washes and totally worth it. No damage or residue. I sound like a commercial bit trust me. Hair Masque - Professional Hair Mask Products by Kerastase