I average 13-16 overall. I get stuck in stop/go traffic on the highway a lot, and some city driving, otherwise I do tend to drive it like I stole it. We'll see what the 545RFE upgrade does, and for curiosity I'll have to go easy on the gas pedal for a tank and see what that does.

 

13-14 bout same with 35" as stock without mods. 75 Suburban with 454 no od got same.11 with 10000 lbs behind it. 350000 mile before selling it.

 

I'm curious too - any of you guys getting over 17 MPG live in a 'hilly' area? Or mostly flat?

I live in KY - 90% of the state is hills, and that's when my D gets real thirsty, I can almost hear it gurgle the fuel on a couple of hills around me - kinda like the older fat guy posting this... hehe

Seriously though - when my wife was in school for a while - my D was eating more gas than I did going to work. The drive was roughly the same distance, but to get her to school - I had more hills and in comparison they were far bigger hills than I run into going to work.

 

i live in a pretty hill area, (at least by my standards), i live at just under 500 ft, most places i need to get to are at 1000-1500ft, its all up and down, the trick is to use the DOWN to save as much fuel as you can, put in a lower gear (lock out OD, put the shifter in 2) to let the engine to the braking, this reduces the amount of fuel being burned by the engine because the weight and momentum of the truck will keep it turning with less fuel being consumed.

im sure having the 4.7 under my hood really helps me out in the gas dept.

 

I have a 5.9 here, and right now I am getting 15.3 mpg. I average around 15 usually, but on a day when I'm in a rush it can go as low as 12.

I think it's entirely how you drive these trucks - when my dad drives, it goes down to around 12, but I've had her as high as 21 (all hwy, but this is pretty good!). My highest 50/50 was probably 17, right after my tuneup and oil change.

If your mileage sucks.. replace the plugs, change the oil, and go a bit lighter on your right foot!

 

Holy cow, driving ms.daisy? Jk but I only wish my 5.9 got that kind of mileage. Even driving nicely around town I'm lucky to squeak out 13mpg and 16mpg hwy. Of course having heavy tires does not help.