Welcome aboard!
How many miles on it? Do you have maintenance records?
I'd put money that you're overdue for spark plugs, PCV valve, differential and transfer case fluids. Throw the gamut at it and your MPG should go we up. I get 12.5-13 city (lots of traffic lights on my commute) and I'm running much larger tires and a bunch of extra weight. I sometimes squeeze out 15 on the high.... bricks don't like going fast