as for the origional question, please!, with 31's regearing would not only be a waste of time because obviously if your not lookin to go big on tires ur not lookin to go big on the trail (not an insult of any sort) so regearing would lower your gas milage, which seems to be your main concern. in actuality, on the highway you may even see an increase in mpg due to the larger radius tire (math, larger radius, larger circumferance, more distance covered per rotation at constant speed) but may also see a decrease during local driving. 31's ll be fine fer wheelin and daily driving, dont werry about regearing till 33's if you want all of your torque back