The 2012 has the 6 speed tranny, I have had three of them and the six speed is getting a hair better mileage than the 5 speed... what the guys posted before me is right on the money.

my 2012 will be for sale very soon, it is a Laramie with 10k in extras. guy before me did it and then gave the truck up with 3k miles says it rode too hard. it has the carli suspension on the fornt and it rides like a caddy

 

My 2010 PW with 305s on it gets around 13.5 on the highway and Im lucky to get 11 in town. But I didnt buy it for the gas mileage.

 

I had a 10 and that is right on the money

For 60 bucks get the molar echo meter that is made by auto meter it plugs right in to obd2 port and has instant mpg and allows you to find the pw's sweet spot for fuel economy.

My 12 with 325's actually gets 2mpg better at 72 mph than at 68 mph