bad fuel mileage tuned

[Mxer_99]

Well after a long time of using this forum to help educate me and slowly get my truck the way i like it i have now had my first problem and am turning to you guys for help. I hope this is in the right place if not go easy this is my first post! But I bought my truck back in the beginning of june and drove it about a week before i decided to do the dpf delete the egr delete and a 5in turbo back exhaust. I decided on an sct livewire with the kem 345 tune and it has been flawless ever since that is until maybe three months ago...During the summer my truck was getting around 19 hand calculated on the hwy which is where most of driving is done. But as the weather started to cool my mileage started to drop and not just a little it went down alot! As of right now the truck is getting 12 and if i hook up to anything it drops to 10 or worse ive changed the fuel filter and it did not help at all. I had a tuned 6.0 for several years and this truck is a totally different animal. So right now i am at a loss of what i need to look at and why. Any ideas on what has happened with this truck? I forgot to mention im in arkansas so winters are typically very mild and summer is very hot!

[Mxer_99]

forgot to mention its a 2008 f250 ccsb it has a 5in lift on 35in tires

[bentstroke_02]

ya winter fuel

[F250Marine]

I would almost put money on it, that it the winter fuel. I was averaging about 19 during the summer and now I'm down to about 15 and my truck is stock height. You could try running a additive and see if that helps any. Also check your air filter.

[Mxer_99]

I run an additive in my truck year round its just hard for me to believe that it would drop it as much as 7-10mpg i could believe 3-5, but cutting my mileage almost in half is killing me

[Doss]

Is it really cold where you live? I'm not certain, but I believe these trucks add fuel to get up to temp a little quicker when cold. Also, people tend to let the truck idle more when cold.

I know winter fuel has dropped mine a few MPG, but 7-10 is a fairly large drop.

Check tire pressure and air filter. I know it may not explain it, but it could be part of the problem. Good luck.

[bentstroke_02]

I live in Ks and mine drops EVERY winter

[Alaskan_awd]

It's most likely a combination of winter fuel, longer idle times, high idle to warm up, and colder air is more dense so it has to compensate by injecting more fuel.

12 does seem low though, I run H&S HD300 tune as my daily and I have been getting around 14.5 - 15 average over the last few months, mostly highway and that is giving it plenty of time to warm up before I drive it.

[K1LLsW1TchEd]

Yikes, 7-10 mpg drop isn't good. Have you serviced the truck ie: oil and filter change, also fuel filters change? Is your truck going into high idle, you may have a faulty EGT sensor which will raise your idle even though regen is disabled.

[Mxer_99]

I had everything serviced a little over a month ago and no difference. My truck never really high idles but i just noticed today while my truck idles it misses periodically every ten or 15 seconds and its just one little miss and something pops under the hood when it misses, sounds like it is coming from the passenger side