If the gear ratio you use is chosen to complement the tire size you choose, there should be very little change in fuel consumed. If you start with a vehicle that comes stock with 4.10's and P235's (approx 29 inch tires), then change to 33 inch tires, you have increased your tire diameter by around 14 percent, and at the same time, you have decreased your mechanical advantage over those tires by the same amount. That's why if you change to larger tires, you notice a decrease in power and performance, as well as a drop in fuel economy because you have to struggle to turn the tires.
But, after changing tires, if you change your gear ratio accordingly (in the example you would need to increase the ratio by around 14 percent, to 4.66), the driveline would perceive very little difference compared to stock. As there are no 4.66 ratios available, so far as I know, you would either have to chose 4.56 or 4.88, the most common combinations in that range. If you have an automatic transmission, you could go with the lower of the two and your torque converter would make up the difference most of the time. If you have a standard transmission, you could go with the higher ratio and do just fine, although your rpm's would be just a tad higher on the highway than stock, not usually a problem when using larger and heavier tires.
The idea is not to chose a gear ratio you want to use, but chose tires you want to use, then adjust the gears as needed to compensate for the different tires. Because torque is produced by the engine, not the tires, the torque will remain the same ragardless of your gear ratios, but the gears will dictate how well you can use the torque you have.
