Just another update . . . I am at 4200 miles on the odometer. Mpg are 30.0 during the week (90 of my 100 mile commute is highway) and it drops to 29.4-29.7 on the weekends with city driving, though I only drive about 20 miles on weekends.
I have reset the computer just before getting on the highway and gotten up to 38mpg; however, the 29.4-30.0 shown now is the cumulative total for the past 1200 miles. My own calculations (miles divided by gallons at the pump) support the trip computer.
Maybe I am a much more defensive driver than others getting lower mpg readings. I use 87 octane, obey the speed limit for my "city driving" and cruise control at 70mph on the highway. No jack rabbit starts, coast to slow down in traffic instead of brake, etc. In short, I drive every car I've owned like a 90 year-old!