I'm running a 99 Drw and getting about 14.5 mpgs with 355 gears. I have two buddies that have the same truck running 410's and they get 20 mpgs. I find it hard to believe. Yeah it takes more to get mine going but is it really that big of a difference? Should I swap to 373's.? What is the best setup for this truck?
MPG also has a lot to do with driving habits, gear ratios, tire size, transmission and many other things. I had a 01 6spd speed with 3.55's and my buddy had an 01 Auto with 4.10's. Bone stock he usually got 1-2 mpg better than I did. But I am also 32 yrs old and he is 57 yrs old. Our driving habits are totally different.
Now if you do much towing you will like 4.10's or a higher gear ratio.
If you are doing a lot of in town driving don't look for much more. I was avg around 16-17 in town with my 3.55s however when you get them out on long runs that's where the high gearing helps. I could see any where up to 21mpg just depending on driving habits when I went on long trips
Are you talking straight highway long-distance, mixed, start-stop around town? Being more mixed mode leaning to start/stop would explain it. Taller gears only translate to better mpg on the highway, all else being equal. Higher gears means worse fuel mileage in urban environments with a lot of start-stop driving.