I have been running full synthetic in my Jeep 4.0 since I got it at 93000 miles ... never ran the same oil twice. I try to stick to a 5w or 0w if possible for cold starts. Last oil change I used T6 5w40 in it. Seems to be doing well (except for my oil filter housing leaking). The 4.0 seems to like it and it doesn't make any funny noises. The problem is ... it's no longer at any local wal-marts. I try to avoid supporting Wal-Mart if possible, but it's the cheapest 5w-40 by far. Is anyone else missing this off of the shelf at the local Wal-Mart?