I follow the truck manual guidelines. But sometimes change sooner than later.
Most important for me is to drain fuel from frame filter bowl, collect fuel in clear glass, inspect fuel for contamination. Do this frequently, every month. And buy fuel from stations I hoping trust.
I don't drive often (5 yrs and 62k miles so far). And visit Ford web or Sync site, record fuel check in my truck maintenance data. Keeps my record and Ford folks honest if they question any maintenance records of this vehicle.
Stopped at a out of state station, seen tanker truck getting ready to dump fuel in tanks. I asked if he dumping diesel, told me not yet, doing gasoline at the moment, but will wait on diesel dump till I fueled up. Clearly he knew why I asked. Thanks.