I seem to get 19-20 around town no matter what I do. I think they lowered the rear gear ratio for fuel economy. The .224 in the rear is NOT the correct gear for this car. Way to low, car doesn't even wake up until 65mph.
My manual calls for 91 octane, but 'round these parts we have 87, 89, and 93 octane available. I run the 93 octane just to be safe.
I am not sure that I would run the 89 octane even if I thought I could - since 93 octane is about a $.10 more than the mid-grade, and I drive 15,000 miles a year, at 20 mpg I am using 750 gallons of fuel each year, times a thin dime for each gallon, $75 extra a year to make sure I run the good stuff. Cheap at the price for peace of mind.
Anyone have comments about running too low octane in the tank? I feel sure that the fuel injection computer would dial back the timing a little to compensate.