also don't go by the overhead its really not that accurate, and it could be that it originally had 17" rims on and now its got 20"'s making it even more inaccurate

my 05 with 20's gets about 12 city and 16 hwy, if i drive like grandpa i can get 13city and 20 hwy, but the way i drive i get about 10 city and 12 hwy lol

 

I have an 08 Bighorn 4x4 with stock 275/60/R20's and I average around 15.6 according to the overhead. In city only I do around 10-11 MPG, on the highway it will do around 22 MPG if I set the curse. I've seen it as far up as 24 but it's rare. It generally sits around 15-16mpg if I don't reset it (114 mile round trip to work, with 40 or so stop and go, with lots of hills).

As it stands, my truck is stock with the factory CAI, I've been to broke to do to much to it, but I plan on making a few upgrades to try to get a little better MPG at a later time.

 

My console is pretty accurate, I have double checked the math, although I have never been able to hold the 22mpg rating long enough to confirm it. Keep in mind I am running 265/70/17 tires that are more a street tire that an A/T and aftermarket lighter 17" rims. Also, my truck is actually couple inches lower than stock which give it bit less wind drag. Yes I did reprogram the ECU for the new tire/wheel size with my DSP tuner. I also keep my truck extremely well tuned up.

 

i get about 10 when i drive around town here on e85... however on my trip from michigan to virginia i was amazed to get about 20 miles to a gallon! with 5 people and a bed full of music equipment! it was a miracle! must be them 3:55's

 

The O/H is useless. There is only one way to calculate fuel mileage. Anything over 18 mpg is wishful thinking. I can't drive slow enough to get that. If I run ~80 on the interstate (is there any other speed?), I get just a pinch under 15 mpg.

 

I just finished off a tank this week and to my surprise I got 16.9 mpg. My truck is an '04 Hemi w/72K+ on the odometer, stock other than a cat-back exhaust. This was at highway speeds of 68-70mph using cruise about 75% of the time. And yes, I manually figured the mpg and didn't use the overhead, although it was scary close on its estimate. The overhead was reading 16.4 mpg.

I got 420.9 miles out of 24.9 gallons of gas. Simple math equates to 16.9 mpg. I was surprised and happy to see the figures.

 

Although I am no longer a 3rd Gen owner I must say I am quite impressed with the gas mileage of my new truck. I've heard stories of people getting 20+ with Hemis on the highway.

Old:
2006 Ram 1500 QC SLT Hemi 2WD
3.92 20's with 33" tires
CAI, T-stat, E-fan, DSP, Magnaflow exhaust
Averaged 17 on the interstate at 70 if I'm lucky.

New:
2009 Ram 1500 CC SLT Hemi 4X4
3.55 with 17's and 31" tires
DSP is the only mod
Averaged 19.5 on the interstate doing between 65-75 driving to FL from NC.

 

That's pretty decent, I think. At least for these heavy trucks. I won't brag about my Honda Civic's mileage - lol.

I may be a little an*l about it, but I record my mileage every fillup. So far, I'm seeing 12-13 with the truck around town, but I'm fully stock and I do enjoy planting my right foot down on the Hemi from time to time.

 

i have a 2003 hemi 4wd and i only get 13.5. I have a cai and magnaflow exaust 100000 miles on the truck

 

I know this thread is 2weeks old now but for others looking....

Plugs are due every 30kmi. Sure you may get away with running them for longer but your mpg's and performance will slowly dwindle without you even realizing. Changnign plug wires won't increase performance at all on a stock engine. You would need other supporting mods such as a higher voltage ignition box.
With that said, I get 14-15mpg on average ONLY because i have Superchips tune with transmission support. Without the advanced trans support, I was getting 13.5mpg on average.
For a 2004 wit higher mileage..your at the industry standard as far as mpg's go.

I would only suggest using basic copper plugs. Nothing fancy. You'll need 16 plugs for a Hemi.