An old timer race horse trainer told me he always put used motor oil on his horses hooves. I don’t think it made them any faster or did wonders for their feet. That trainer is now dead at the age of 54. I wouldn’t really follow much of his advice.
With the technology we have now I would be sure to buy some of the hoof conditioners that they sell at the tack stores or online that the companies put a lot of money into testing before they sell it.
There is a reason it is illegal to dump used motor oil in the garbage or on the ground. Would you put it on your kids head or fingernails?