I hear ya man.

But the MPG doesn't need time to "catch up". Thats not the point of disconnecting the battery...

And yes, when you fill up with 17.8 gallons you got 17.8 gallons. What i was talking about is the trigger that turns off the pump when you're full. That trigger is not as controlled... so one pump may put in 17.8 gallons but another pump will put in 17.2 gallons or 18.5 gallons. So if you went 270 miles "on that tank", depending on which pump you fill up at you could get a reading of 15.1, 15.7 or 14.6 MPG respectively. In other words, the amount that you put back in the tank isn't always the same exact amount you used.

In the end we're splitting hairs. It's not a matter of life or death... There's just that analytical PITA voice inside of me that's always nagging me. That voice goes a bit haywire in my head when i read someone post that their hand calcs are more accurate than the computer calcs, because when you start breaking down the variables involved, its really not. But it's also not going to be an order of magnitude off or anything... so yeah, im just going to go drink a beer and watch some hockey now