It's worth considering, as well, that if you're planning to push the four-cylinder model to its limits, your mileage won't be any better in the real-world (perhaps lower) than that of V-6 models. But if it's mostly light commuting you do, you'll find better mileage than in GM's full-size hybrids—the Chevrolet Silverado Hybrid and GMC Sierra Hybrid.
The 2012 Toyota Tacoma is one of the few trucks with a base four-cylinder model. And as such, it's pretty good on gas, with ratings for base 2WD four-cylinder models returning up to 21 mpg city, 25 highway. On the other hand, 4WD V-6 models are considerably thirstier at 14/18.