Where I live, it is quite humid in the summer and quite dry in the winter. My hair hates this. I thought I'd give deep conditioning with olive oil a try.
My method was pretty basic. I poured some olive oil in a ramekin, to have a more manageable amount to deal with and poured it on my dry hair and massaged it in, then poured some more in and massaged it in, until my hair was completely saturated with oil. I let it sit for twenty minutes and then shampooed and conditioned my hair as usual in the shower.
Verdict: No difference at all. Save you olive oil for cooking because it's not going to help with your hair.