I adjust all my calculations to include tire diameter and confirm them with GPS. I get about 10.5-11 mpg around town in LA. When I go on long trips I stick to about 65 mph and get about 16.5 to 17 mpg over say a 1600 mile trip to Kansas City. Keeping track of my MPG since I installed the 305/70/16 KO2's (32.8 inches) I have averaged 12.65 mpg overall. Keeping in mind that LA traffic is a MPG killer. When I stayed in Kansas City for 5 weeks, I averaged close to 15 mpg, due mostly to the traffic being much lighter. All of these numbers are far better than I expected prior to my purchase, because the EPA estimates were so low.
Dang, I live in Kansas City and can't seem to break over 13 with mixed highway and city. Also running 295/70r18 tires so I realize this number isn't an actual reading. I must have a pretty heavy foot though