You can't just look at axle gear ratio and determine reliable fuel mileage, there are several more important factors to consider first.

Average speed
speed fluctuation
# of stops/starts
Weight
Tire size
Transmission
Power

These are the major variables that change from one or our trucks to the other when comparing fuel mileage.

You will be better off with a set of 3.07 axles and a decent tune on your pump if your commuting long distance at steady slow speeds in an empty 2wd truck. especially with stock tires and a light foot.

If your interested then compare rpms from different gear ratios for a given speed and see where you are:
http://www.grimmjeeper.com/gears.html

 

Thats the thing I don't always drive nicely haha and would putting bigger rims and smaller tires on do anything?

 

yeah it will make ride harder . If your looking for mileage then the stock pizza cutters are hard to beat.


Are you talking about running your D250 or the new W350?

I used to get very consistent mileage with my D250 with the pump maxed, I would have swapped a 3.07 into that if I wasn't afraid of it breaking and not being able to find parts. There is more than enough power to handle extra gear ratio with a stock engine.

 

Darn but the stockers are so ugly haha

 

my truck (read discription below) the best i have ever gotten was 25 miles to the gallon, granted i put 400 miles on it in one day, but average in town is 18-19, and highway average was 21-23

 

Thats pretty darn good!