Originally Posted by Unfairkickazz93
While I agree the 8-speed is a much more advanced transmission; I do have to disagree on you claim that the mpg highway is better. They managed to get 2mpg better for various reasons i.e. grill shutters, lowering air suspension, electronic power steering, etc. I do have to say there is less parasitic loss in the transmission so that will help a little too.
Id have to look into the EPA's testing procedure.
I'm not sure if they use loaded up vehicles for MPG tests.
Their tests are clearly flawed as they don't distinguish between the base vehicles and loaded up ones, nor do they distinguish between gear ratios.
Clearly, for example a 2013 Hemi Laramie Crew Cab with 8 speed auto all the options and 3.92 gears will not get as good of gas mileage as a
2013 Hemi SLT Quad Cab with 8 speed auto, no options and 3.21 gears.
But look on the window sticker and they will both say the same.
You are correct that their will be some improvements because of the slightly better aerodynamics of the 2013, as well as grill shutters and air suspension.
However, your thinking is also flawed, since the 2013 with 6 speed auto gets the air suspension, better aerodynamics, electric power steering too yet the 2013 MPG ratings are the exact same as the 2012's.
Also, the changes would be tiny. The grill shutters and slightly more aerodynamic 2013 will not be enough to get 2 mpg highway improvement.
If ANYTHING, it may be .75 to 1 mpg.
Combine them with the more efficient 8 speed auto and that's probably why it gets 2 mpg better.
It also gets 1 mpg better in the city and that would be fully attributable to the 8 speed autos better gearing, because at that point, aerodynamics doesn't do much when puttering around at city speeds.