2nd tank 57 mpg,

You'll need to gather a few more "data points" before you can really say... most people see up to a 2-3 MPG difference between the computer and calculated. With the car being so new, it's possible that the bladder is stretching out a little with each pump, meaning you're putting more gas into the car than you actually used. Give it a good 5-10 tanks and look at the average difference after that, see if the number starts going down.

If it continues to be such a large difference, try filling up at a different station for a few times... it's possible that the pump you're using is misscalibrated, rading slightly higher than whats actually going in... but it really is too early to tell, given the inaccuracies of the bladder.

 

Averaged over 40K miles of record keeping (yes, it's a weighted average), my MFD reads 1.7 MPG higher than actual.

However, on a tank to tank basis the difference can be huge because the fillups are so variable.

 

<div class='quotetop'>QUOTE(Tempus @ Sep 28 2006, 08:04 AM) [snapback]325031[/snapback]</div>

Over the first 16k miles I'm in the same ballpark. My MFD reads 1.1mpg (or 2.4%) higher than actual.

 

Also note that outside air temp can really play Old Harry with your calculations on a tank by tank basis. If you live somewhere with large temp swings you'll find that your calcs are wildly off because the bladder has become more elastic or less so since your last fill up. Like other folks have said, over the long haul these sorts of variations should average out.