Oily and Dandruffy Mane and Coat HELP!

My yearling thoroughbred stud has had this issue since the day I got him. He was very sick as a foal and weanling and the people I bought him from I threatened to call the ASPCA on a few times because of his health and the condition of the rest of their horses ( I ended up buying him because I didn't want to leave him). He is now healthy and looks absolutely beautiful other than one issue. His mane is probably the worst. He has a very oily mane and tail and all down his body where ever you run your hands you get a decent coat of dandruff. He's had this issue since I bought him and got him healthy again. Right now he's on a quarter of a scoop of Buckeye Growth formula since my mom's Friesian/Oldenburg filly is on it (and I just started giving him it to keep his weight up for the winter) he also gets a full scoop of sweet feed to go with it. His weight is and body condition are perfect for his size since he is a rather large baby at 15.1 hh at a yearling. He is brushed better than most professional horses on a daily basis in an attempt to help this problem but it's not making much of a difference.
Any info or recommendations for supplements to help with this would be appreciated.

Are you sure his diet is completley balanced, with all of his minerals? Lack of minerals can lead to dry skin. I have heard washing his mane with an oatmeal shampoo, and then applying conditioner, then eucalyptus oil into the roots of the horse’s mane to rid it of any fungal infection helps get rid of it. After that, every two weeks, give or take, repeat that process.

As Casey said give him a balanced died. Wash him twice a week or so with a horse shampoo. I find "mane and tail" works very well with my horses when it comes to oil and dandruff. Good luck!

Sadly I cannot wash him especially at this point in time. It's getting close to winter and way to cold to think of any sort of bathing.
I think I am going to get my vet to look at that when he comes back out to reassess my boy's eye. Ulcerated Cornea -.- caught it very early though so that was a plus.

That is a problem. Im from Florida so I don't ever think about the cold. Just see what your vet has to say.

Yeah Michigan kind of sucks for about 6 months out of the year. -.-

Try (when you can), bathing him in Listerine, that is what they use here at William Woods.

Funny because I've heard of that being used on horses that tend to scratch their behinds on everything. It has a numbing agent even though its not strong but it stops the itching.

I get what you mean I was thinking about adding if it isn't to cold, but forgot. It is not like it is really threatening your horse's health, unless it is some strange unheard of disease that that's the only sign, but I highly doubt that Today we are having one of the best days in the year here, it is going to reach 60 and yet we are at the beginning of winter. Yep 60 is hot for us, 70 happens like every other year! And yes, I live on the coast, but riding on the beach is what you sacrifice for crappy weather!

Its about 28 and just started snowing here as of an hour ago. But its just slightly concerning that he has this dandruff all over his body and his mane and coat are just oily and gross.