If one were predisposed to it, the dash readout is more easily manipulated based on when you reset it last.
My trip 1 I reset more or less every tank, and shows recent economy.
My trip 2 I havent reset in a very long time, and is very close to what feully says.
I guess inaccurate is not the appropriate word to use.
2012 Frosted Glass SFE (9/1/11-current)
2003 Pitch Black 2.3L Focus SE (RIP 2/19/04-8/17/11) (261,503 miles)
2000 Twilight Blue 2.0 Focus LX (RIP 6/10/01-2/7/04)
1987 Light Blue 3.8L V6 Thunderbird (RIP 6/17/01)