I've had a few friends who have had various versions of Jeep products, and each one of them have said those engines seem to piss Mobil ONE and other synthetic brands of oils....
so Pennzoil is a good choice for those type of engines...
It has a crappy Pep Boys reman 258 in it, and even new those things were not known for having effective valve cover gaskets... can't wait to blow it up so I can swap a Ford 5.0 or GM LS motor in it...