7.5k Motorcraft 5-20 syn blend and Motorcraft filter. Never even had to add a qt between changes. 96K on it now. Even on my old jeep, after it hit 150k I rarely changed the oil, and the engine was still the best part when I got rid of it at ~280k.
I use Mobil-1 5W20 Full Synthetic changed every 5,000 miles. I've heard good things about Penzoil Platinum's line of full synthetic oil and how they make their base oil from natural gas instead of crude oil so I'm thinking about trying it out next time around.