I went from getting 18-19 mpg to 14-16mpg on highway and i have done nothing different to my driving. i have replaced the fuel filter and ford rebuilt the tranny since i have noticed the decrease in mileage???? btw its a 2004 F150 FX4 5.4l 3v supercab with 57k Any ideas? i was thinking about changing plugs. I have only had this truck since 51k and new to ford and to be honest dont know where the plugs are lol anyways Any pointers or ideas on why such a decrease would be helpful

 

Depending on where you live, you could be getting winter-blend gas already. I've experienced the same drop around this time of year before. I don't know the exact reformulation, but MPG typically plummets once there's frost on the pumpkin (and I don't mean the rear diff!)

 

Check for a sticking parking brake...I believe there was a TSB for this on 04-05's and some 06's

 

I'd say it's winter gas and colder temps that are the likely cause for your mileage drop. 17 to 15 is what my truck drops to here in NH.

Now if you live in a warm climate, I'd wonder if that drop was based on a single tank or a few tanks of gas. Could just be a crappy batch of gas.

 

before you attempt to change the sparkplugs do some searching through older posts, seriously. For some people, myself included what used to be a simple spark plug change can turn into an expensive nightmare fast. Just thought you should be forewarned. Hope you figure out the drop in MPG too.

 

I wonder if it can be as simple as a dirty air filter?, have you replaced it or checked it lately? when i went to B.C. from ontario i got around 18mpg average and on the way home changed the air filter and slowed down alittle bit and got 20 most tanks

 

i have replaced air filter fuel filter oil change (amsoil) right after i bought it. Only thing i'm thinking is i'm out in the dakotas working and they have that 10% ethonal junk which is 89 oct and i ran one tank of that and went back to 87 unleaded but have ran 3-4 tanks through it since then. One thing i'm gonna do is have the dealer change plugs when time comes. thanks guys i will do some more research on this also

 

sounds like its the gas that is your problem.


you get good MPG during summer months, and then the winter blends show up...I can normally expect about a 2 mpg drop with that stuff

 

before i got stationed in Colorado, i was in the Carolinas, had a 04 4x4 f150 screw, had a CAI and an edge programmer, i was getting around 18 in the city and 20 to 22 on the highway. well got moved out to Colorado, started getting 14 to 15 in the city and 17 to 18 on the highway! thought i was going crazy, then i noticed that this tree hugger state's got E85! it's got alot to do with the fuel your state is saling!! Any way check the gas. I since traded my old F150, got an 08 f150 4x4 screw lariat, get arounf the same mileage, except when i get the high octane which is 91 here, or i put the injector clean in. So i got another CAI and a programmer on the way, should be here in about a week, will let you know more after it comes in.

 

Ya i figured it out...... these farmers in North dakota got on their knees for the good ole oil company and now the 87 here has 10% ethanol go figure..... cheaper by 15 cents and burns more.... i'm gonna start running higher oct if it means my gas mileage back.....

 

winter blend i'm pretty sure showed up here two weeks ago....my gas mileage dropped 1.5 mpg

 

I run 87 with 10% eth and I get 16.8-17.5mpg with my 08 screw 4x4 5.4 Ive also gotten better mpg when I drive long dist with cruse on.....