alright, i have a 97 5.4L f150, nothing done to it but exhaust ( true dual ) and my gas mileage is s***. On 87 octane i get 5, no lies, 5 mpg. on 93 i get 9-10. I do not drive it like i stole it or anything like that, this truck never sees past 2500 rpms. So far i've replaced Fuel filter, plugs & coil boots, air filter, checked back pressure, its with in spec. , and i still have no idea. any help what so ever would be greatly appreciated.

 

o2 sensors?when was the last time they were replaced?the frts should be done every 30k for ultimate results

 

the o2s were checked with a dinoagnostic tool, they did not appear to be lazy or anything, should i still replace them?

 

my 04 van has over 100 k miles on it ,every 30k i change mine when i service my air filter-the only issues i have with gas milege is about 1 mpg less on the ethanol blended fuels in the winter-phil

 

How exactly are you calculating your mileage? What type of driving are you doing? How many tanks are you basing your MPG average off of?

 

number of miles on the trip counter from the time of filling up at the station to parking at the station divided by number of gallons put into the truck

I drive like an old man,

One tank, or should i change that?

 

According to fueleconomy.gov

1997 Ford F150 Pickup 4WD

Automatic 4-spd
8 Cylinders
5.4 Liters
Regular Gasoline

EPA MPG
12
City

13
Combined

16
Hwy

 

My 97 F150 4.6 auto using 87 octane
gets over 310 miles on 20.8 gallons.
Fuel running out lite on for 15 MPG.
Drive normal to soft. 20 degrees out snow,
winter gas ??? in PA.
Stock truck 83,000 miles.