Would I get any gas mileage benefit by switching the differential to a lower gear ratio? I hear people talk about going to 4.88s and such for off roading, but what about going the other way for people whose runners never see anything but the road?

 

The idea is to keep the motor in its peak torque range in the conditions it sees the most. If the motor dosen't get to run in its happy power band it will use more fuel. Lower RPMs dosen't always mean less fuel being used. Both excessivly low and excessivly high RPMs wil burn more fuel than necessary. Its probably best to stay with stock gears if you run stock size tires.