If I create or purchase an oil with a harmful spell like say Magic Missile. Can I throw it as a splash weapon?
[...A]pplying an oil requires no special skill. The user merely removes the stopper and ... smears on the oil.
[...U]sing an oil is a standard action. The... oil takes effect immediately. Using ... oil provokes attacks of opportunity. An enemy may direct an attack of opportunity against the... oil container rather than against the character. A successful attack of this sort can destroy the container, preventing the character from... applying the oil.
A creature must be able to... smear on an oil. Because of this, incorporeal creatures cannot use... oils. Any corporeal creature can... use an oil.
[...I]t takes a full-round action to apply an oil to an unconscious creature.
Oils are for smearing not throwing. An offensive oil would have to be smeared on an unconscious creature. (And most characters won't want the weird reputation that comes from smearing oil onto their downed foes.) The rules don't even consider trying to smear an oil on a conscious, unwilling creature, nor do the rules cover trying to pour a potion down an conscious, unwilling creature's throat.
A reasonable house rule would allow a creature to subject a grappled or pinned victim to oil-smearing or potion-pouring as a full-round action that provokes attacks of opportunity (not usually from the grappled or pinned victim, obviously).