Thanks for the update, Antony.
FYI, there's a second fuel consumption gauge in the MID (or a setting... I forget which) that let's you display a long term result vs. auto-resetting short trips.
Mitsu's EPA ratings for this car are conservative.
24 owners posting at MirageForum are beating the EPA on average (collectively around 41 mpg US, with a high of 59 and two stinkers at 29). Interestingly, the manual drivers are doing better than the CVT owners, despite the CVT'S better rating. A slightly older analysis...
MirageForum Fuel Log stats: 19 Mirages, averaging 42 MPG, 17.9 km/L, 5.6 L/100 km
Could be for a variety of reasons, but one of them is because the manual is simply rated more conservatively than the auto.