If you want to worry about MPG, don't go with a full sized truck. Now, I got the 5.7Hemi with a LOT of engine mods. This weekend, I decided to try to get as good fuel mileage as possible on my trip to the north GA mountains. I averaged 18.7 MPG on that tank of gas being very light on the gas pedal and trying not to use the brakes. Lots of highway miles on that trip but also lots of winding mountain roads being on and off the throttle a bunch. My usual is 13.2 MPG. My driving is an even mix of highway and city driving. Get around 16 MPG with light traffic, but only around 12 MPG in heavy traffic. If I let my truck warm up for 15-20 minutes on cold mornings, I average around 12.6 MPG per tank of gas.

 

i have an 04 hemi 4x4, the best ive done is 16.2 and the average is about 15. thats whith city and highway combined. now i am light on the throttle, i try to keep it below 2k rpms. but sometimes i horse on it just to hear my exhaust. if you can drive "normal" they really arent too bad. with winter here and the gas blend, im going to be lucky to see anything near 15 but im sure as hell going to try.

 

I guess it depends how much highway / city you drive. I had the pleasure of having one of those beastly 3.9's in my 98 ram with 4 spd auto and also in an older Dakota. City was probably about 3-5mpg better than my current hemi with stock 3.55 gears. Highway was basically the same over 65mph. Below that, the V6 actually got a few mpg more. Based on my experience and along with other posts, I think the highway mileage will be similar across the board but if you drive a lot of City, the Hemi wouldn't be my first choice striclty from a mpg point of view. It's the most expensive V8 in the city I've had over the years including my old Fird and Chubby. That being said it's still my favorite V8 and easily out hauls the others I've had.