All my horses manes to that, some worse than others. I've wondered that myself, but just never took the time to try and do anything about it. You might could oil it and band it, but I don't know how long you'd have to leave it in there for it to stay.
I had a lady tell me to smear vasoline real heavy on the mane. I just can't get past thinking what a mess that would be tho, to clean up. I've tried bands, and braiding, but it seems that breaks off more hair then it helps.
Becky
I use mane tamer on mine. I found out the hard way not to use it before riding though:')