Just recently had both plugs and coil packs replaced. Plus a new napa computer all done by the dealer. I'm disappointed in the MPGs I'm getting. Now mind you I know I'm not looking for 30mpg out of a 5.4 but I used to get 17 to 19 on the Hwy and I'm lucky to get 15 right now. Just curious as to what might I look at doing. I did change the fuel filter and cleaned the MAS and throttle body.

 

Four wheel drive?
Super Crew?
Winter gas blend?
Change to more aggressive/larger tires?

 

My 07 4x4 SCrew had a miss on a couple cylinders. I changed out the boots and springs on them and a new coil on one. My fuel mileage went down quite a bit. I ran some injector cleaner through it and it has improved a little bit. Im attributing mine to the winter blend of gas. Also how are you reading that mileage?

 

2007 screw 4x4 5.4

 

Well just by the computer in the truck

 

I do have a more aggressive mud time about one size up

 

Did you disconnect the battery when you did the plugs, resetting the fuel mileage? If so do you do more hwy or city driving? What percentage of each would you estimate? How often did you reset your mpg on the dash before you did the plugs?

 

Honestly....that sounds about right.
I have a 4x4 SCREW and get 14-15 city.
17 HWY. With a slightly larger tire

 

I get 17 mpg hand calculated in my rwd FX2 Supercrew and thats 80% driving 60 mph on the highway on a 22 mile commute to work.

 

Heh... last 90 days 10.573 MPG for me.... I'd be ecstatic with 15!