</font><font color="blue" class="small">( Is the gas mileage related to the AWD?)</font>
Apparently. Like a WWII Jeep, the un-needed axle turns at road speed all the time.
</font><font color="blue" class="small">( Is it full time AWD, or can you switch it to 2wd for fair weather driving?)</font>
The ordinary A/T model is what I'm familiar with. Its a FWD car with a clutch pack claimed to provide 15% torque to the rear axle continually. (until slip is sensed).This can't be ideal for efficiency.
When the going gets slippery, however, is where the little rig tears off its shirt and reveals the Superman side of its personality. It is impossible to spin a front tire until there is so much torque applied that traction is broken at the rear as well.
Mild offroad, same thing. I've noticed down in the back of the orchard if the weight is on two diagonally opposite tires and one front wheel starts to spin getting started up the grade (disked, uneven soft ground), that front wheel can't turn even an inch before the front/rear clutch is engaged solid and we start moving without drama. You never feel it, it's engaged before you sense it. Same thing at road speeds.
Attached photo: I was packing down earth at a washout (on a steep downgrade) when my fill gave way - leaving the tire dangling over space. I stuck a limb under the tire and forced it up, then put that rock back under it. That loaded enough weight onto the diagonal back tire that I simply backed up out of the hole without wheelspin. I bought the A/T specifically because you can make a gentle start offroad, sort of an imitation low range. This would have been impossible with the MT version.
Sorry for going on and on here. I really like my Subaru. Seventh 4x4 I've owned and I'm still amazed what it can do.