Castor oil? For hair?
I'd try olive oil or coconut oil first.
They do wash out much easier (remember - this stuff will be going down your drain) and leave your hair soft.
(Just looked it up).
I guess it's more popular than I thought.
A little oil can help condition your hair, but if you want your hair to be healthier overall, you have to watch your nutrition.
For double speed hair growth (I usually grow 1/2 inch hair a month - this helps M. grow 1 inch hair a month) try taking daily:
1 tablespoon black strap molasses (sulfur source)
1 teaspoon FOOD GRADE diatomacious earth (mix it into juice or water and drink it down) (Silica source) and
1 biotin supplement
Warning - this not only grows hair on your head but all your hair (leg hair, under arm hair, bushier eyebrows) will grow fairly quickly as well as your finger and toe nails.
Hair problems can be a sign of thyroid problems - it's worth getting it checked out.
Other things you can do to help your hair is never heat it (no curling or flattening irons and I only blow dry my hair on cold if I can't let it air dry).
Dyeing it often can fry your hair.
I had to give it up but then I switched to henna and it covers my grey well and I love the auburn color I get from it.
Hope your hair feels better soon!