Also most oil unless virgin is rancid, may not look so but has very little goodness in it.
But you can feed coconut oil as it is very different, as long as it is virgin cold pressed, but you have to be careful of mycotoxins.
But I know that Coolstances copra feed is safe as I feed it although if you have high levels of iron in your area or your horse does it may cause problems, I have had no problems with it at all
Horses can digest the right sort of oil, but they do it via the liver and not all oils are digestable for them, but the more natural format the better. I just allow my horses to choose, if they like it they have it if they turn their noses up then they don't need it. BOSS are good to feed but you have to becareful of where you get them from as some are covered instuff for birds that causes problems to horses, birdcoat is one name. Also some horses can not tolerate BOSS either it depends on trial and error ass what suits one may not suit another.
You can get good virgin coconut oil at a good price in the USA but check it is virgin and taste it yourself to see if it is ok.