Why is my fuel mileage worse?

[Chasin' Tail]

Installed mods in my sig and now my 6.4 gets worse mileage, stock tune, driving easy on 250 nothing helps. I wouldn't complain if my fuel mileage had stayed the same but to get worse, while researching before I bought a tuner I had never read of someone getting worse mileage after tunes, any ideas, I think I just wasted 1600 bucks.

[Gunny_990]

Possibly winter blend fuel, cold weather, just a thought

[08stroker250]

Are you hand calculating worse mileage than you hand calculated stock? Or are you going off of what your dash says.....

I feel like I would really have to try to get worse fuel mileage than I did stock....maybe a few passes down the 1/4 mile track on a tank of fuel would net me worse fuel mileage than I got stock.

[wired1]

the worst i've gotten yet is an 1.5 mpg increase being tuned, and that was hot rodding around and longer idle times due to the temp lately with winter blend fuel. avg increase for me is 3 mpg. and my LOM is only .5 to .7 off on the high side of my hand calculating. I know idle time affects my mpg, how long if any do you let it idle?

[Chasin' Tail]

I'm going off what my truck says, it seems like I am having to fill up sooner, usually idle time is 5-8 min.

[08stroker250]

What tune?

[Chasin' Tail]

210 and stock so far, 210 seems to be a little better.

[391dman]

Diesels get worse milage when its cold out. Did you just happen to throw this chip in right when it was getting colder?

[Chasin' Tail]

Originally Posted by 391dman

Diesels get worse milage when its cold out. Did you just happen to throw this chip in right when it was getting colder?

Yep, End of Nov.

[superdutydixie]

mines getting about 220 miles per tank of winter blend right now. stock, all city drivingand long warm ups(Alaska). I hate my life right now. haha