I have a 2011 F150 5.0. I bought it with 96,000 miles. It has 162500 on it now. It has never got very good mileage ( best 15) now it's down to 11. I had an 09 with the 5.4 that would get 16.
IveI seen posts where guys get high teens and low twenty's with same truck. Any really ideas of what the issue might be? Thank you

 

When did you do a tune up? That means change plugs, COPs, etc.

Also, fowled O2 sensors can do some odd things too.

 

Has it been lifted? larger tires? those two things will kill gas mileage. Keep the tires properly inflated. Drive it easy. The right tune will increase gas mileage a little. Put a couple bottles of Gumout with PEA or Chevron Techron in the gas to help clean the injectors.

 

It's also quite sensitive to axle ratio.

 

minimize idling
coasting down to a stop
easy on the throttle


all of those are driver modifications, that can net serious results, much more than any tune up or modifications can help with