As I said earlier, I am averaging 30+ by the app on my iphone......still smiling ?I've found the vehicle MPG can be easily gamed. If you stomp on it for the first 1/2 tank, then baby it for the next 1/4 or so, you'll get really good mileage on your EVIC, but it will be quite bad for real. The same goes the other way - baby it for 1/2 tank, then get on it until you fill up, the EVIC will read a bit low. That's resetting the MPG at every fillup. Over time it might average out a bit closer.
On average, without playing games, my EVIC reads about 2.5 MPG better than reality. That's with a 2.1 MPG for SD. That means ~85% (or more) of the EVIC readings are too high. That's a wide variance, so really all I can say is the EVIC is optimistic. ...by a lot. So when I see someone post a 30+ MPG EVIC snapshot, I just smile.