Steadly decreasing fuel milage

[Dooley rig 29]

So bought this truck a month ago 100000km on it. Its an 07 6.0 . It had awesome power and decent fuel milage,5.6km/L. 10,000 k later its lost some power and fuel milage was down to 5.3 ,so i replaced the fuel filters(yes there ford) and had ALL my power back but NO gain in fuel milage, now 3 days later its lacking a bit of power again and milage is down to 5.2....Filters are still clean, fuel and driving habits are the same. i run diesel kleen every other tank. from the last few hours of reading i am leaning towards bad ficm or failing injectors.... any thoughts from the techs? oh btw thats about 12.3-12.4 mpg ...sorry im in canada guys

my 06 kingranch with 37's chiped and done to the nuts gets better milage than this :S

[skanj0]

Originally Posted by Dooley rig 29

So bought this truck a month ago 100000km on it. Its an 07 6.0 . It had awesome power and decent fuel mileage,5.6km/L. 10,000 k later its lost some power and fuel mileage was down to 5.3 ,so i replaced the fuel filters(yes there ford) and had ALL my power back but NO gain in fuel mileage, now 3 days later its lacking a bit of power again and mileage is down to 5.2....Filters are still clean, fuel and driving habits are the same. i run diesel kleen every other tank. from the last few hours of reading i am leaning towards bad ficm or failing injectors.... any thoughts from the techs? oh btw thats about 12.3-12.4 mpg ...sorry im in Canada guys

my 06 kingranch with 37's chiped and done to the nuts gets better mileage than this :S

As I was reading your thread I started thinking about the usual things that can rear their ugly head with the 6.0L and fuel mileage - - - until I got to your signature and saw that you're running 37s. I suspect those are your problem, perhaps in one or two ways. 1) they weigh more, have a higher rolling resistance, and likely have a larger cross section than stockers - meaning lower fuel mileage. 2) the truck may not have been recalibrated for the larger tires, meaning you're covering more ground than your speedometer/odometer are indicating, making you think your fuel mileage is less than it really is.

Lastly, is the fuel mileage you quote hand calculated or from the "lie-o-meter"? The lie-o-meter is notoriously over optimistic on fuel mileage...

[roadrunner]

One problem that gets overlooked is you could have a brake caliper sticking on one wheel causing a drop in fuel mileage. Unfortunately its quite common on our trucks where road salt is used during the winter months.

[Dooley rig 29]

Originally Posted by skanj0

As I was reading your thread I started thinking about the usual things that can rear their ugly head with the 6.0L and fuel mileage - - - until I got to your signature and saw that you're running 37s. I suspect those are your problem, perhaps in one or two ways. 1) they weigh more, have a higher rolling resistance, and likely have a larger cross section than stockers - meaning lower fuel mileage. 2) the truck may not have been recalibrated for the larger tires, meaning you're covering more ground than your speedometer/odometer are indicating, making you think your fuel mileage is less than it really is.

Lastly, is the fuel mileage you quote hand calculated or from the "lie-o-meter"? The lie-o-meter is notoriously over optimistic on fuel mileage...

sorry i should have been more clear on that , my problemed truck has 35's... my king ranch has the 37's and ive had the king ranch for 500,000 k with better fuel milage than my new truck... and its not poor fuel milage im worried about , im worried that its steadily decreasing and lacking power....i work rigs and fuel is free thank god

[Dooley rig 29]

milage is hand calculated and correlated with "lie-o-meater" ,they are very close.
brakes are excellent, nothing is sticking or rubbing or warped

[2003kingranch]

might sound dumb but whats your air filter look like?

[Dooley rig 29]

just serviced all fluids and filters, all ford parts

[2003kingranch]

well your next thing would be to get a hold of a scanner to read for codes or buy an edge insight (which you should have owning a 6.0 anyway) see what the ficm looks like ect...

[Dooley rig 29]

I have the edge insight but its 2000k away at home in my other truck im in the bush right now and sending your truck to ford up here is a joke, i know more about these trucks than they do, hopefully it lasts till the end of this hitch and i get to a real mechanic.....any other "feild" ways to check the ficm

[Dooley rig 29]

wow not one tech willing to chime in....thanks