Is this gas mileage normal?

I have a 2001 Dodge ram 1500 158k miles on it and it has the 5.9L (360) v8 in it. On highway I best at 15-16mpg and town I get only about 10-11 mpg. I know this is a powerful engine but still this seems ruff. Nothing is wrong with it that I know, I keep it up to date (oil, power steering fluid, etc.) The only thing is that the transmission shift into a few of the gears way to fast. I mean I will be in overdrive doing 45 mpg and when I go up a hill or something being that its in overdrive so soon you really have to gas it to make it down shift or else it will bog down, same as going around a curve or something, like when I slow down going around a curve then try and speed back up its still in over drive and I got to gas it to make it pick up speed again.