If I had hydraulic disc brakes on a bike (I don't) I wouldn't worry about baby oil or plain drugstore mineral oil corroding any of the metal parts or attacking hoses and seals. What I would be concerned about is boiling point and range. It may be the same "cut" as Shimano's mineral oil but I wouldn't take the chance unless the specs were nearly identical. As noted,it's a silly place to save a few cents.