Seen this often. The PCM reflash and block heater TSB doesn't do a darn thing. I've fixed more than a handful of them with high pressure fuel pumps. Those have been on truck with a profound oil growth. We're talking ~1 liter/week.
On other units excessive misfires contribute to fuel in the crankcase. Take your pick of root cause ... carbon tracked spark plugs and coil boots, catalytic converters, moisture in the intercooler and CAC tubes, cold starts (these things are dogs to fire at -30 and colder), etc etc
As for the accolades for the 5.0 ..... it's a good mill and all, but I'm curious how many of you have done cylinder heads for misfires on #4 and #8. We get at least one a month in need of one or both heads. The intake valves get so thin that you can shave with them. I've personally done two in the last three weeks - one retail and one warranty. The good news is that it's so common that you can buy a loaded cylinder head for $800 from Ford : )
2003 GMC Sierra 3500 -- dually, 4x4, hasn't blown up yet and that's what i look for in a truck
Ford Doctor -- They come in broken and leave fixed. Ford of Canada Master Tech