Looking at the specs, Toyota says 17 - 22 mpg for the 4 cylinder manual transmission 4X4, 16 - 20 mpg for the V6 automatic 4X4. I normally get 16 - 17 mpg in town with the camper on the truck, 18 - 20 mpg in town without the camper on a 2006 Tacoma 4X4. On the road at constant 65 the mileage is 14.5 - 18 with the camper, 19 - 21 without the camper. Yes, I do keep track of the mileage every fill up. No, I don't drive like I am late to an appointment. I wonder if the 4 cylinder mileage is that much different that you will really notice the gas cost difference over a V6. Just a thought. (As an aside, we own a Prius in addition to the Tacoma.)