I'm guessing that whatever calculates my gas mileage is malfunctioning, but heres the story:
my mileage (according to the truck) around town is ALWAYS between 13 and 14, ive NEVER seen it drop below 13 in the 84k miles ive driven this truck. All of a sudden yesterday it dropped to between 8 and 9. I didnt change any driving habits (i baby it for the most part), its in the same FLAT town of Davis, and i always run top quality Union76 fuel on my Troyer premium tune. So i dunno what the deal is, any ideas? Will it throw codes for something like this?

This next tank of gas i'll be logging amount of gas used vs mileage driven to get a more accurate mileage statement to see if it is messing up.

 

did you have it in 4wd or did you add a new exhaust..i found on my 04 when i put a flowmaster on it it dropped suddenly

 

nope always in 2wd on the pavement, and i've had my flows for over a year.

 

hmm.. i dunno my 04 had the same milage (84000) and i got that drop too...

 

Do you have a lock on your gas cap? The gas thieves are out there!

 

its impossible to siphon my truck. Ive tried. lol.

 

Is there an MPG re-set? Or is it all instant on the F150s?

 

How many miles on the truck, and how has it been maintained?

 

Could be an O2 sensor. I had a similar thing happen in my old truck when just one of the O2 sensors went bad. Truck didn't run noticibly different, but the mileage went in the crapper. Replaced both O2's and everything went back to normal.

 

That might be it, i havent replaced those yet. 84k on the truck, i have kept it perfectly maintained.

 

You can reset them simply by bringing up your mpg read out and simply push reset and it will trip it back to zero and will begin re-averageing you mpg. Note: if you do this the mpgs will change drastically as you stop and go for the few miles until it has a sufficent number of data readings to give it a more accurate reading.

 

What does that have to do with MPG??

 

84k, are you still on the original plugs and cops?

 

yup, ive followed all maintenance recommended by Ford like its religion. I know the plugs should be changed soon, and they will be as soon as i am home from school this summer. i just dont understand why there was an *instant* drop in mileage, not progressional.

 

Your truck hates, plain and simple.