HI -

Is it new, or used? Mileage will increase after 1500 miles, and steady out after 3500 or so, in addition to you re-learning how to drive and getting to know the car's personality. What's your tire pressure? You can run at 40lbs and still be pretty comfortable.

I have found that the dash display will understate MPG if there have been a lot of stop/go or large speed changes, but will generally be pretty close (+/- 0.3, about 1%) on tanks that have been mostly constant highway. Better to be pessimistic, then pleasantly surprised at the pump. It looks like you already understand the concept that each fillup is not to the same level, but that it will average out over time.

Yes it is possible to accelerate on 3, but not from a stop, and it takes a very very very very very long time to get to speed. For instance- in eco mode, it can take ~10 secs on level road to go from 40mph(4th) to 43mph(5th). The gearshift complicates things there, but you get the idea. I've found it better overall to accelerate without regard to eco, keep it under 2000rpm, and let off the gas as soon as you approach the speed you want to hasten the onset of eco mode (~>30 instantaneous mpg). And get into 5th at all costs- pop over 42, and it will hold down to 35 or so.