Yeah, the biggest problems are the 5.7 in an oversized and extra long truck that is also a 4wd so it is super heavy. I bet it is close to 6500-7000 lbs. Hammer pretty much hit everything I was going to say.

 

You could always look around for a beater 4 banger for commuting. You'll easily make up the money in gas and less wear/tear on your truck to justify the cost and cost to insure it.
When my step-dad passed away in '07, I had the opportunity of inheriting his little two door '01 Hyundai Accent. I didn't want it, couldn't justify a third vehicle and would not get rid of my truck or Grand Cherokee daily driver for it, so I helped my mom sell it.
The thing was absolute mint and had 31,000 miles on it, but KBB full retail for the thing was only $2800 (it only stickered for $7995 new), and even with the crazy low mileage on it, we sold it to one of the old man's nurses who was commuting in a big V8 Buick for $2500.
In the couple of months I had use of it, I consistently got 32 mpg in combo (mostly in-town) use and could hit close to 40 mpg on the highway. With the price of gas now, I wish I'da kept it...

 

I can get pretty reasonable mileage out of my Ram by keeping fresh plugs in it, driving like I have an egg under the gas petal, looking ahead to anticipate the next stop light and driving 60-65 on the highway. Everything listed above gets me about 3-4 extra miles to the gallon over driving the truck the way I like to drive it. These are big trucks and they aren't going to get "good" gas mileage, period.

 

One thing you could try, just for schitz and giggles is to reset the PCM, to see if it makes any difference, also it seems the Hemi does not care too much for the Winter fuel blend.

 

Tires, like the others mentioned. These can make a 2 MPG difference easy. Don't bother with the nitrogen filling though, it's a gimmick.

Something you might be interested in that we were discussing in another thread. You can get a propane kit and make it dual fuel. It has its pros and cons, and kind of depends where you live. Sorry, I can't find the link anymore.

 

I feel your pain brother!!! I have the same truck. 06 Ram Mega Cab with the 5.7 Hemi. GAS!!! was my biggest mistake ever. I agree the truck is way to heavy for that motor. If I could go back and change anything it would be to buy it in Diesel. Love my truck hate the motor. Its a great motor for the average 1500 comuter pickup truck driver. But with the Mega Cab we entered a whole new land... the heavy truck land. I do mostly highway driving and I have about 87,000 on it and around town I am doing about the same as you 9.2-9.8. I have tried a few things but nothing has really helped. Sorry brother!!! Wish I could help ya out more. If we lived close I would buy ya a cup of coffee and we sit around and tell horror stories about MPG. ha ha ha do what ya can to enjoy it you have a great truck other then the MPG!

 

The power is there, problem is, they tried to make the Hemi a "one engine fits all" deal. Putting the thing in everything from touring cars to sports cars to heavy trucks. The problem with the thing is the power (torque) kicks in way too high in the rpm band for very much efficiency with a lot of weight.
There are some cams out there that with a custom tune would have the thing pulling almost like a diesel down low, but we're talking big bucks here. Re-gearing to 4.56s helps a lot simply by getting you up into that power-band much faster. I find with the gearing, I get up to interstate speeds with much less throttle than before and can keep it into that 2200-2400 rpm "sweet spot" that the Hemi seems to be much more efficient in.
But again, it's more of a power thing, and although I see about 2 more mpg around town, I give it back when cruising at 75 mph +. Too costly of a mod with not enough mpg gains if you are looking at it strictly from a fuel economy standpoint...

 

I too am in same boat; 07 mega cab 4x2 gas. Best ideas that others have come up with that would actually help would be things like lowering it, reduce its air drag. Bout all we can do though. Well headers, cat back, and intake. Also keep highway speeds way down to help out your total average. I do 76 mile round trips for work, most are highway. The rest are in city getting about every red light. Highway speeds at 55 on the dot on cruise. City, I just granny it. Last tank lasted me 1 full week; 502 miles with a 17.3 mpg average and I still had 30 miles left per the overhead.

 

I have an 06 megacab with about 160,000 on it and I get about 14mpg on the highway doing 73 and about 10 around town. I haven't heard of anyone to much better than that I also have 4wd. The HEMI in these trucks dont like to pass up gas stations.

 

Whats the weight difference between a fully loaded 1500 slt 4x4 5.7 hemi vs the "megacab" 5.7 loaded 4x4?? Megacab cant be that much worse can it??