well, i've only had the car for 2 months, but so far my lifetime MPG calculated is only about 2 MPG less than what the MFD would have me believe. I figure thats pretty normal, as others have posted similar findings. Well, this last tank i go to fill up and the MFD reads 44.5 MPG, but my calculations come out to 37 MPG. I sat back and said wow. Then i figured my bladder finally started to expand (the avg. temperature here in cleveland has increased 10 degrees from the last tank to this one, and from the one before it to the last tank) and i was feeling the hit from that. For those of you who have had the car for a bit longer, do you notice a reverse effect in the fall as the bladder contracts (ie the calculated is way more than the MFD)?
<div class='quotetop'>QUOTE(eagle33199 @ May 9 2006, 12:59 PM) [snapback]252202[/snapback]</div> Yes, the bladder expanding and contracting will affect your current tank's MPG. Keep track of the gallons and maintain a lifetime average and it evens out. At 41k miles, my lifetime average charts between 52.2 and 52.9MPG which is pretty flat considering my lowest tank average has been 37 and highest 61.1.