That is horrible. I get 18-20MPG hand calculated almost all highway miles, and it will drop to around 15 if I am doing mostly in town driving. When I took my family out to Montana towing my sons car we got 10-12 MPG. Towing my boat to Lake of the Ozarks averaged around the same (at 75-80 MPH). Towing weight in both cases was around 4K lbs with 5 people in the truck and the bed packed with gear.

My truck currently has 10,500 miles

 

I get 12-13 city. I drive very conservatively.

Highway is really what I meant. Oldjeep gets 18-20, I get 15-18. It works out to about 18 at 55 mph, 17 at 65 mph, 16 at 70 mph, 15 at 75 mph. I drive nicely.

 

And the gear difference and lighter weight of the 2wd could account for that.

I bought the 3.21's specifically to get the milage up into an acceptable range. I do a lot of towing, but the majority of the time I'm just hauling myself to work. If I really need to tow heavy occassionaly, there are at least a dozen guys in my club with 1 ton diesels that I can borrow.

I also drive fairly conservatively, fuel saver light is on a lot of my highway travels. Jumping on the throttle, while fun sometimes really makes a difference with the thirsty Hemi.

 

When I pass on the highway, I plan ahead. I will gain speed slowly and then pass vice pushing the pedal down and watching the rpms jump.

I was thinking for my next set of tires I want to go with a bigger size to help offset the 3.92's. The only problem is that my current tires weigh 40 lbs and I can't find a 34.5ish size tire under 52 pounds. I am afraid that the increase in wieght will destroy the fuel savings of lower rpms.

 

I'm not too worried about gas mileage as right now i only get about 8-9mpg in the city and about 11-12mpg highway driving. So pretty much anything is better. the truck i was looking at had the 3.55 but i was thinking about getting the one with the 3.92's. I eventually want to put a lift and bigger tires so they would help out alot

 

Wow! That is horrible!

I am not complaining one bit, but if you don't need the 3.92's, you will save gas buy getting the 3.55's or 3.21's.

Then again, my 13 and 17 are not bad numbers for a 5600 lb (crew cab) truck.

 

Mine is all stop and go city traffic. Last trip to the in-laws I set the cruise on 70 and after 200 miles I filled up and average 20.2 hand calculated. I have no fuel saver light in mine and the roads are average with streches of hills (some large) and streches of flat.