You work the average out since around Jan 2002 - its hard enough typing all this in ! REAL LIFE MEASURED economy (speedo/odo checked with GPS) 7/91 EB XR8 auto 3.27 diff and just under quarter of a million k's..... Its pretty obvious the difference between Sydney peak hour from western suburbs, and a bit of easy cruisy driving (above 60Km/h).....
Oh yeah - Optimax or Caltex premium always (Both seem to work OK) Have installed the factory Trip Computer, and for the last two tanks has been .1 and .2 out from measured consumption - pretty accurate in other words !
(And yes, I do keep all the receipts....)
You can take your ergonomically designed, space age, computer controlled, 4 door, cup holding map lighted split double wishbone split fold down retractable cargo covered moon roof piece of transportation and keep it. For I have felt the thunder. And I know the difference!!