In my 2002 F-150, 4.6, for the first 60,000 miles I only ran Motorcraft 5W-20 and the FL-820S filter. My OCI's ranged from 5,000 miles early on to 7,500+ miles as the miles accumulated. I just switched to Havoline 5W-20 synthetic and a Fram Ultra synthetic oil filter. I'll use the filter for 2 oil changes. I switched to the Havoline synthetic because it was about the same price as the Motorcraft oil at an Advance Auto oil special. Looking in the oil fill the valve train is almost spotless. My wife's 2005 4.6 Explorer with about 165,000 miles on it ran Motorcraft 5W-20 and the FL820S filter for 5,000 mile OCI's for the first 75,000 miles. It was under extended warranty. After that I run various full synthetic oils and filters for 8,500-9,500 mile OCI's. It's also clean inside the valve train. Neither burn any measurable amount of oil during the OCI and the oils always come out no darker than a dark amber.
Whimsey