I don't ride city, so it's hard for me to comment on that. But, I do ride rural country highways and backroads...and some interstates. I consistantly get between 48-50 mpg's using 6th gear @ 2000 rpm. So that comes out to 55-65 mph on 2 lanes, and 72-75 on 4 lanes. All I have is SE slip-ons. My best friend gets the same!
my 08 rk, was averaging 42mpg. all stock except for tommy gunz slip ons. now I'm averaging around 46mpg. thats riding two up 90% of the time. have around 9600 mi. on the rk. seemes to be getting better mpg as the engine gets broke in.
I have to admit I'm not that concerned with mpg on my bike.
however it is a good indicater of how well the bike tuned.
2005 fltri with se air cleaner,rinehart true duals and harley download nets me 46 mpg
mixed riding or highway.
08 Ultra
103
Screaming Eagle A/C
SERT
Supertrapp Slip Ons
I get 37-40 mixed with about a 50/50 split of 2 lane country roads and city. I got 43.7 on the highway at 75ish. Haven't really gone on a trip that is exclusively 2 up so I can't tell you what that is...