Here's the scenario...I changed my Delco fuel filter with a new AC Delco filter at the end of September (thanks Eric, for the instructions/pics)...old one went approx 23K miles (opened it up and it was black :eek: ...will now change at 10K) but I was still getting around 16 - 17 mpg city.

Mileage dropped to 14 mpg after the fuel filter change (have filled the tank 3 times now and the mileage remains around 14 mpg).

Nothing anything else has changed in my world...primed the new filter, ss bleeder is snug, started up right away after the change, still using Stanadyne at every other fill-up, tune wasn't changed on the programmer, getting diesel at the same station (Flying J).

Any suggestions as to the drop in mileage? Only thing I could think of was possibly that the fuel is now winter diesel.

Thanks in advance.

Your right foot..? :D

Sorry, couldn't resist, I don't have a good answer for your question.

winter fuel like you said????

i dont know, mines crappy all the time so i cant really help you... sorry.... :HiHi:

btw, love the sig line....

x2 on the right foot... I've noticed myself pushing a lot more into it after I changed my FF; I never noticed how much power it slowly lost as the old one got restricted.

is that the normal mpg for winter fuel for u?

After the first fillup and bad mpg, I made sure my right foot was in check...didn't make a difference.

Last year's mileage all winter remained around 16 mpg.

Like I originally said, nothing else has changed except a loss in mileage after this fuel filter change.

Truck seems to run fine otherwise and tire pressures are good.

I have no explanation for the decrease in mileage...maybe I should've put back on my old fuel filter :D

Winter fuel

i have no other explanation than winter fuel. did you get a loss in mileage at other filter changes?

ULSD winter blend, heaver foot??

winter fuel for sure, but i've been using 'stanadyne lubrucisity' not the performance additive, work great 4 me.....

Is your mpg's hand calculated, ot are you relying on the dic..?

I'm actually calculating by hand and DIC (hand calculation is higher mpg). However, the DIC reading is a good "heads up" for me if there's a significant drop in mpg to investigate.

I changed my tune back to stock on the weekend and switched back to tow on Tuesday just before filling up...mpg seems to be back to normal again (so far). Do not understand why this would "fix" the problem but I'll keep my eye on the DIC still for a couple more fill-ups.

billygoat7c...my previous filter change did not yield a drop in mpg.

Thanks for the suggestions everyone.