A good tune up and check your tire pressure and alignment, and if you have an overdrive transmission, try using your overdrive whenever possible to reduce your RPMs for a slower revving engine gets better mileage than a high revving engine.
ha! i wish the gas came from venezuela..! we import it with botes undercover that stuff is like race fuel... i dont know where valero imports the stuff we get at the pumps from but its crap!! smells like kerosine!
ok guys im gonna do a tune up and see if it makes a difference thanks!
Definitely make sure to check the timing, whether or not you decide to do the tune up. Might also want to run some injector cleaner through the tank and maybe seafoam the intake.
Even by replacing all of the parts mentioned by the other members the 4.9L has never been a high MPG vehicle so do not expect but a bit more efficiency than you are currently getting.
Boon
Postscript: I will be astonished if you ever reach 15-16 MPG.
15-16 is very achievable in a single cab 2wd. If you get that engine tuned up right you should be able to approach 20mpg, although I doubt you'll hit 20.