Back in the '90s I used to have oil treatments when I went to the hairdresser. They involved sitting with a hot towel on your head until it was cold and were the only thing that ever stopped my hair from being really dry. Do hairdressers still do these? The ones I've been to seem to offer moisturing treatments instead these days but they don't work nearly so well on my hair . I have tried VO5 treatments at home but either they're not very good or I'm not very good at doing it!
GGM - you need Indian hair oil! I use Vatika. at weekends I massage in, leave for an hour or so (wrapped/unwrapped) then shampoo and condition as normal. you can buy it from Asian shops or in the 'ethnic' food aisle in the supermarket. failing that pure coconut oil, almond or olive oil is great too.
Kerastase Elixir Ultime is a fab oil treatment. I have dry hair and use it either as a pre-shampoo treatment or pre-blowdry treatment. You massage a small amount into the ends and mid-lengths. I only wash my hair every other day and use the oil on day 2 to revive dry locks if needed.