[mcrews]

Good job!
1. Depnending on amount of freeway driving.....larger diameter is better. When it's all citty...not so much.
taller tires have always worked for me on the 2002 Q45 and the 07 Kia Sportage.
2. As Barry says....look for a composition that offers lower rr.
3. If there is room go w/ the taller tire (after judging #1)
4. While a taller tire is moving a small amount of the weight farther out, the real concern is when someone wants to increase rim size to get to a taller tire.
5. Need to be taller by at least 5% to have a noticeable gain in mpg.

on the issue of weight:
1 lb static is worth 4 lbs moving(rolling) so more weight is bad. Mainly because of the increased wear on the suspension parts and brakes.
Lowering weight for better mpg is not really effective.
Foe example: remove your spare and check your mileage against having it in the trunck. Bet you $1 there is no difference......and the spare is 40-50 lbs. or 10lbs a tire.......

Now maybe on a truck.......but not on a car.
think about it....how much smaller diameter do you have to go to gain a 10lb reduction????
Now look at the rpms at the smaller diameter.