There is not much you can do to increase the fuel efficiency of this vehicle. Its a 2.5 ton mass of steel and its takes fuel to push it down the road.
About all you can do it make sure its maintained properly, the tire pressure is correct and the tires are the proper size (oversize tires waste fuel). Using synthetic lubricants can achieve a small increase but it will likely not be noticeable. Typically its in the 0.4-0.6 mpg.
Btw-All the after-market products out there suggesting they can improve mpg are just using clever marketing to lure you into buying their products and when you read the fine print you find disclaimers like this from K&N:
We certainly understand why it is theoretically (look this word up and you will see its a snow balls chance in hell) possible for a consumer to experience a mileage increase after installing a K&N air filter or intake system, however, we do not go so far as to make a general claim that our air filters and intake systems will provide an increase in mileage.
There are just to many variables that affect mileage such as: tire inflation, the type of fuel, weather, elevation, the speed at which you drive, the gear in which you drive, the speed with which you accelerate, engine maintenance, excessive idling, cruise control, the grade of motor oil you use, and of course, the condition of your air filter. In short, mileage is complicated.
Yet despite this disclaimer there is bound to be some who will chime in here and claim the got a 1, 2 or more mpg just installing an air filter and air induction system.