Horrible fuel mileage

[Daxman]

Does anyone know what would cause my fuel mileage to drop by about 3 MPG. The last 3 weeks i have been driving really easy so i can save some money and it seems like its backfired. Im getting around 8 miles per gallon now. The ford dealer installed a brand new ficm so i dont think thats the problem. It doesnt make any sense. Checked the air filter and it seems to be clean so if anyone knows what could cause this, please let me know.

[saltlake3fitty]

6.0s dont like to be driven "easy", that could be your problem, do you have any boost leaks?

[05 smoker]

what is your maintenance like. fuel filter, oil change,etc. how does the truck drive performance wise? does it pull like it should or does it feel slow.
everything like to be driven easy just make sure you open it up once in a while to keep the turbo vains free.
mike

[MO05SD]

Originally Posted by Daxman

The ford dealer installed a brand new ficm so i dont think thats the problem. It doesnt make any sense.

Most likely the dealership may have reflashed your ECM/TCM to the latest strategy when they installed the new FICM and never told you about it. This happens all the time from what I have read. This generally causes a loss of 2-5 mpg most people say.

[Daxman]

The truck drives great, i dont hear any weird noises or anything. As far as maintenace schedule, i change the oil every 5000 miles and the fuel filter every other oil change. I actually have about 10,000 miles on this set of fuel filters but thought that was fine because the truck does run fine. I open it up at least 2 times a week. I also add the ford cetane booster everytime i get fuel. I havent checked for any boost leaks yet. I odnt know, i will fill it up and calculate the mileage again. I know of all the horror stories with these motors so i the maintenace is always done.

[RatherBNtheWoods]

Originally Posted by MO05SD

Most likely the dealership may have reflashed your ECM/TCM to the latest strategy when they installed the new FICM and never told you about it. This happens all the time from what I have read. This generally causes a loss of 2-5 mpg most people say.

Yep. I lost MPG's and power/torque, but at least the turbo lag got a little longer!!

[Daxman]

How can i check the ficm update, should i take it back to the dealer and have them flash it again.

[MO05SD]

If you know anyone in your area with a programmer-EDGE,SCT or others. They can read the strategy you are running. The dealership can tell you also. Don't know what they would charge, but I wouldn't want most dealerships to check mine. Spent to much money going to earlier strategies and wouldn't want to lose them. Truck run 200% better and mileage has gone up 2-3 mpg from when I originally bought it.

Can't say 100% that it is why your mileage has gone down. Just have read a lot of post where trucks have gone to dealership for minor repairs or maintenance and owners say they lost 2-3 mpg. Confronted dealership and they admitted to re-flashing truck while there without owners consent.

Beings they were installing a new FICM. They had to flash it and probably re-flashed ECM/TCM to match with latest flashes.

It's just my .02 as to what may have happened.

[legionxxii]

If you have a SCT or a friend does hook it up and check what the FICM strategy is if not contact for ask them what strategy they put on the FICM. I would then contact PHP or IDP about having the FICM rolled back to a better strategy bring your MPG back up and more power. Also custom tunes will also help with MPG



EDIT: beat me to it

[Daxman]

I dont have an SCT and most of my friends with trucks all drive chevy's :,... the SCT tuner is the next thing on my list. I guess i will call the dealer tomorrow to see what exactly they did.