I have a 2005 f150 5.4 4wd. I got it new 8 years ago, and have figured out my mpg on every tank of gas that's gone in it. I have always got 16.6 average, and I drive it pretty hard sometimes. I recently had some work done, though it did take 2 shops to do it right. the first shop changed 4 plug and 4 coils, when I got it back from them, my mpg dropped to 13, and they didn't even fix the problem that I took it to them for. So I took it to the dealer, they did the other 4 plugs and coils. Runs great, but I'm still getting only 13 per gallon no matter how easy I am on it. Any ideas?

 

it could be the gas your using has more ethanol. Try finding no ethanol fuel see if that improves.. Could be your area has winter blend now..

 

It happened in the middle of a tank. When I asked the dealer they said the same thing. So I have run 3 tanks of 100% gas. No difference.

 

Could be leaky fuel injectors.

https://www.f150online.com/forums/v8...ram-07m08.html

 

yeah it could be.

 

If it smells lik gas a few minutes after you kill the motor then this will be it. Mine is getting really bad milge right now too and iv heard its something to do with the winter mix they use. Also, if your computer was reset and you haven't taken any long trips then this could be why. It averages your fuel over every time you drive. If you reset your computer and hop on the freeway for an hour you will see better fuel mileage on your display then you would if you reset your computer and do a bunch of small stop and go trips to the store.

 

I do the math on every tank, I don't have the computer display of mpg. This is now my 4th tank of 100% fuel and this tank was at 11 mpg. I was told to disconnect the battery to reset the computer, I left it unhooked for 36 hours and it seems to have gotten worse. I've checked the fuel rails and filter for leaks and they seem to be dry. I just changed my oil and it didn't look like there was any gas in it either. I'm now driving my old beater f250 since it gets 14mpg.

 

I figured it out. It was the new tool box that I had just put in it. I took it off my 150 and put it in the 250. The last 2 tanks have been 16.9 and 18.1.

 

That seems like a huge drop for just a toolbox. How much did it weigh you down?

 

Full of tools like mine, could be 3-400lbs