I have a 2011 Ram Outdoorsman 1/2 ton, 4wd, 5.7 Hemi, crew cab short-box with 3.78 gears, it does have the variable valve-timing system that drops down to a 6 or 4 cylinder when the power is not needed. I keep a book on my vehicles and every gallon of gas that goes in it is hand-calculated, I have found that the computer estimation is about a mile per gallon on the high-side, if it says 18 I really get 17 or so.
But to the subject - I have 44,000 on it and in-town (which it rarely is) I get around 15-16. On the highway I have gotten as high as 22 mpg but for an average it is more in line with 17-19 and recently it has been closer to 19, perhaps the motor is getting more broken in and working easier.
Now the bad news - I had to replace the factory Goodyear Wrangler 6-plys that came as original equipment on the truck and found that they are not available over the counter. I put on Toyo AT's which I have on a couple of my other vehicles and it looks like I have lost about 1 to 1-1/2 mpg but the Toyo is a 10 ply and a more aggressive tread so I am not too surprised by that.
My 2 prior vehicles were a 99 and 2003 Chevrolet 1/2 ton extended cab, 4wd, anytime I got 16 on them I was smiling. The Dodge is hands down better than the Chevrolets - better ride comfort, a ton more power, but it is also 8 years newer in technology.
drover
