No hills around here. 95% city driving, averaged speed Id say 40mph. I was going to swap out the wheels today but it rained super hard so, maybe tomorrow or the day after, lol!

I will hopefully net my 16.0mpg with the 265/70/16's. I have some aluminum tubing and what have you for an intake tube, I just lack space because of the clutch fan and shroud.

 

95% city driving is going to be putting you right where you should be. And as already stated, your getting better MPG than your calculating because with your speedo being off, (even a little) your going further per tank than you think.
Get those tires on or adjust the speedo, and you'll probably start seeing 15-16 in your calculations.
Those taller gears actually help you in the city too.

 

How many miles are on the truck?

 

on my 2003 ECSB 5.3/4L60E/3.42 stock 235/75 16 tires and aluminum wheels, i have 07 efans, stock air box and paper filter, dynomax ultra flow muffler in place of the stocker, rest of the truck is bone stock and i do mostly city low speed driving and i get on average high 14's to mid 15's MPG, and thats with occasional freeway trips of about 65 miles each way, truck has alittle over 70K miles and MPG went up alittle with the efans, didnt notice anything with the muffler.

 

Exactly. I totally agree.

14mpg is fine with your truck in city driving. But definitely get that PCM tuned for the right size tires you have - OR get the proper size tires on your truck.

 

14mpg in city may be fine for you guys but its not for me. I want at least 15.5 in city or its getting a for sale sign put on it. I do about 20miles round trip a day with most of it being 35mph cruise set. Turns about 1200rpm youd think itd sip gas like a 4cyl. Im putting my stock wheels on tomorrow, havent had time recently. I would like to ultimately get 18mpg in cityis that possible? Thanks for your help guys!

 

get an efan if you do that much city driving, you'll see a nice increase in mileage.

 

I wish I could average 14mpg in town. I spend more time stopping and accelerating than I do at any speed. My city mpg is ~11 and highway 17 if I just cruise.

 

I bet that all that stopping and starting would kill mileage. So no one yet has answered my ''Q'' is 18mpg in city acheivable? if so what mods would I need to get that mileage?

 

there!

it may be doable it may not. every truck and driver is different.