ICDEDPPL

iTrader: (1)

NOT!

9.7mpg 100% HIGHWAY if I keep it under 66mph.. (completely empty)
8.2mpg if I throw in 20% stop and go.

6-7 mpg towing my boat.
4 mpg when I get off the highway.
Then they throw in a tiny 26gal tank so you have to refill ever 30 minutes .

Replaced both 02`s and MAF still the same.

Thats %$#@ING retarded. I will be going to back to Diesel as soon as I can thats for sure. I find myself leaving the truck at home and taking my wifes little ****box because this thing eats gas like no other trucks I`ve ever had. None of my companys 3500series vans loaded with tools and equipment even come close.

8.1l blows!!!

wannabe

Icdappl- I tuned mine with a Hypertech. I have 4.10 axles and get 11.5 mpg empty in my Av 2500. This winter I am getting 10 btw. Towing I get 8-9 towing the CAT. Do you have AC plugs in it?

Wannabe

Knot 4 Me

2500HD? That is quite a bit worse than the 2, 8.1L equipped 'Burbs that my buddies own and tow with. How tall/wide are the tires?

BGIII

iTrader: (3)

Highway mileage sounds about 1mpg low, everything else lines up pretty close to my experience. On the bright side, the 8.1 engine never gave me a single issue in 8 years. 26 gallon tank is BS. The Yukon is brutal with a 38 gallon tank. If you are getting these numbers off the computer, don't ever do it by hand. You can knock about 1mpg off of everything the computer says in my experience.

Unlimited jd

iTrader: (5)

I have both a v10 ford and a 7.3 powerstroke. Diesel fuel here is so expensive $50 actually goes further in the v10

ICDEDPPL

iTrader: (1)

Its a 3500 dually..... I put a AFR meter in the rear o2 and I`m getting 13.9 on take off and never see better than 14.5 afr.
Mild thunders 454 is glued to 14.7 unless he gets on it..
But, if that Mileage sound close to what everyone else is getting then I`ll stop chasing a ghost.
thanx for the replies

MILD THUNDER

iTrader: (3)

Yea, on my 1997 454 dually, when the wideband is installed in the rear o2 location, the truck really doesnt vary readings from 14.7, unless i go to wide open, then it drops. But anything below that throttle position wise, at maintains a pretty steady 14.6-14.7. Even accelerating from a stop light, shifting thru the gears, its 14.7.

Icdedppl's seems like its overfueling, then the 02 is seeing this, and eventually trimming the fuel to get back to target. Any change in throttle position the AFR takes a dip, then slowly works its way back to 14.5. If i remember right, thats what I was getting on my wideband, at initial startup, when in open loop. But as soon as it warmed up a tad, steady AFR.

Any thoughts?

Sydwayz

iTrader: (1)

The MPG of the 8.1L are all over the internet; it's no surprise.
They did purposely leave the MPG numbers off of the window stickers though.

And a LOT can affect fuel mileage, so trying to do any comparison is pointless.
gearing
drw vs. srw
4x4 vs. 2WD
fat wife vs. skinny gf
empty vs. a few tools vs. fully loaded
towing mirrors vs. regular mirrors
windows down vs, AC on
bug deflectors
tire size (height)
wheel size (diameter)
tire size (width)
wheel size (width)
windshield visor
tonneau cover vs. open bed vs. cap vs. van body
lift vs. stock vs. lowered
4speed M32 auto vs. 5 speed Allison auto vs. 6 speed manual
Driving Style (biggest variable)

The best I got out of my 2002 8.1L with 4.10 gears 4x4 2500 Avalanche was ~14 mpg--all highway.
That was bringing it home to VA from FL when I drove it off the lot, bone stock and brand new. I pulled the 4x4 stickers off the fenders somewhere in the Carolinas which probably netted me .000000001 mpg in reduced drag.

----------

Do you have an aftermarket intake and/or filter?
You might try going back to stock.
More air means more fuel which = less mpg.

paintman

I cant offer anything because I keep staring at your 2 avatars...but I think you mentioned a 8.1 gas mileage not to bad when she's parked...but I cant focus

08 fastech 292

I had an 8.1 in my last Suburban, past tense. Best I got was 14 mph highway around 8-10 around town. Towing was always 8 mpg towing my 271 Formula. Plenty of power but the gas mileage was not a strong point. Now that I have a 2500 HD d'Max I'll never go back.

Dave