I have a 2005 F150 5.4 L, 4x4, supercrew with 33,000 Km which I've had since new. I got 600 Km per 125 L tank when I bought it, and was told it would get better after breaking in. I got the same mileage in the city or on the highway, if anything it is actually worse on the HWY. According to the ford fuel consumption guide I should get around 1000 KM on the HWY and over 600 in the city. Now that the truck is almost 3 years old I am barely getting 500 KM to 125 litres( again hwy doesn't make a lick of difference), and at todays gas prices it sucks( no pun intended). According to ford it should be burning 12L per 100Km HWY, and 16-17L per 100KM city gas consumption, I burn 25L/100KM city or HWY( this works out to 9.7 miles per gallon). I take it in and they say nothing is wrong and to try different gas, I doubt that would make much difference. It also doesn't seem to be performing/accelerating nearly as well, and hesitates when you press on the gas and actually accelerate( actually have to wait a second or 2 before the vehicles accelerates when passing a car on the highway)Does anyone have a clue what could be wrong so I can get this fixed before my warranty expires next week. I know the mileage is getting worse because I record the KM's I get out of every tank I fill since I bought it, and it is getting worse. Like I said I have very low KM's, never speed or accelerate or brake hard, and get regular oil changes. I also have a KNN air filter and tonneau cover now, no help. Please help me and my wallet!!!

 

with what you're describing (also hesitation) it could be the wrong gas/air mix and the ignition timing.you could have the mixture checked and possibly reflush your computer for proper timing of spark...just the thought...