I have said before I feal 2200-2400 rpm isnt ideal for highway mpg, so I to feal a 6th gear / overdrive would be nice for ~1800 rpm at 70 mph.Autostick or not, after I shift into 5th my Challenger feels and sounds like it has another gear it needs to be in (it's like you're in 4th and need to shift into 5th. It is a 2011 R/T auto. Thanks.
Be more specific, at what speed are you at what rpm, to make you feal you need speed 6? This way others can compare to see if they are seeing what you feal.