I don't know if corn oil is good or bad, but I've had many (like 4 or 5) horsemen that I know which have fed it to their horses and they shine and keep weight and look amazing like no other.
Will I try it with Sky? Probably not and that's my choice. If it worked for your horse, maybe it's worth going back to? I'm not sure.. I like to research what I'm feeding my boy rather than just go off of a few people's opinions (which I'm not saying you did..)
"Strength is the ability to use a muscle without tension"