"Oil Change Required" Instrumentation reset help
 

2009 F250 gas 5.4 litre engine.
Each time the truck is started "Oil Change Required" is displayed on dash.
Oil has been changed twice since this display has popped up.
Manual indicates that warning will disappear once oil has been changed.
This has not occurred.
I can temporarily make display disappear by pushing reset.
Problem is that next time the truck is started "Oil Change required" is displayed again.
How do I reset instrumentation so that this display does not appear each time truck is started?