wider tires decrease mileage?
 

Just wondering how much running 285 square would decrease my gas mileage from stock. Sort of thinking if running square do I can totate my tires and them wear evenly as opposed to changing 2 tires at a time more frequently. It would also allow me to save on alignments since I would be changing tires less frequently.

You'll be losing gas mileage because of extra rotational force needed to spin the wheels... That's kinda only on the rear though, the front will just be added weight

Two reasons

Higher rolling resistance - affects hwy mileage most
Higher inertia - affects city mileage most (or any transient condition)

Tire weight, width, and compound will all affect MPG to some extent. From what little I've seen on the subject, it's not that much difference. If you were driving an econobox and going for max MPG, it would matter. If you're driving a sports car and handling has a higher priority, not so much.

Take 2 cylinders with different heights and roll it down a ramp :)

So any estimates on how much loss I might be looking at going frim stick to re-11s square 285. Wondering if it's worth it or not for the pros mentioned above.

Try http://www.google.com/#hl=en&q=tire+width+vs+MPG