2007 F150, 4.2 V6, 102K miles
At 24K miles I dropped the pan, changed the filter, and welded a threadolet onto my pan for a drain.
After that, every 24K-30K miles I would drain 4 qts. and add 4 new qts.
At 72K miles I dropped the pan again, new filter, and 4 qts.
I finally got around to doing my drain/add 4 qts. today. It looks as if I need to do a fluid exchange.
At 24K miles I dropped the pan, changed the filter, and welded a threadolet onto my pan for a drain.
After that, every 24K-30K miles I would drain 4 qts. and add 4 new qts.
At 72K miles I dropped the pan again, new filter, and 4 qts.
I finally got around to doing my drain/add 4 qts. today. It looks as if I need to do a fluid exchange.