My 2008 CRV consistently tells me I'm getting 1.5-2 MPG better than actual calculations done in Gas Cubby report. I polled the CRV boards (and my God is that the saddest place on the Interwebs or what... shudder) but so few people consistently track their fuel economy or do it correctly I didn't get a good sense.
Why/how would it do that? I use consistent methodology for tracking mine. Same station and even pump as often as possible, my weekly routes are usually more or less the same, my driving habits are regular. I dunno.
FYI - car computer tells me 22.8 MPG, Gas Cubby says 20.7.