Haven't had this problem on a Tib, but did on my wife's CM Santa Fe. Was definitely a bad valve cover gasket which is very common on the 3.3L V6. With our alternator at the back it could be the rear valve cover.
Have this problem currently and fixing it as we speak. Don't put it off either or else you will get the flickering abs/battery lights or even outright alternator failure from it from the hot oil dripping into the alternator.