Welcome to the board.
Does your commute mean you have to go back and forth from Rockford or just from Schaumberg?
For some reason, Toyota seems to overstate the CITY mileage estimates, but not the HIGHWAY mileage estimates. Perhaps they don't know what's it's like to be sitting under the L in snow in the morning.
Nevertheless, Fidgits is right about the computer.
You can thank Cook County for your gas quality.