In my Explorer I use Mobil 1 Full Synthetic with a Fram Extended Guard filter. The filter is designed to be used for 7k miles which is how often I change the oil unless I go for a weekend of off roading then I change it when i get home.
In all the other cars and trucks I have i use Mobil Clean 5000 with the same filter, and I just change it every 5k miles.
The one thing I suggest never putting in any vehicle is Pennzoil.
Daily Driver - 1999 Ford F-150 4x4 Off Road - Soon to have Snoway plow
Trail Rig - 2000 Explorer Sport - 5" lift, 35x12.50's