Do 4X4 trucks use a lot of gas?

If you are comparing two trucks of the same make, model, and year then yes a 4x4 will consume more gas due to the extra weight of the axle, transfer case, additional drive line, and heavier front suspension, as well as the increased friction that the additional drive train causes. However if you get stuck in a two wheel drive truck you will be wishing very much that you had a 4x4 regardless of the cost of gas!