Ok I've played around with this a couple times, but it doesn't seem to work out.

Let's say I am driving at 30mph. I reset my trip meter and acellerate for 1 mile with the MPG pegged right at 30 mpg (halfway between 20 and 40).

Then, after 1 mile, I feather the gas pedal and settle in at 60mpg cruising. I hold 60mpg for 1 mile.

So, 1 mile at 30mpg, 1 mile at 60mpg.. and at the end of the 2 miles, my average MPG reads around 38-40mpg.

Now, shouldn't it read 45?

I tried this a few times after noticing that if I acellerate and my average MPG moves down .4mpg (clicks down), then it takes a LONG time to get it to "click back up".

There's been times where there's been, say 100 miles on the tripometer and I'm getting 51.8mpg.... then I get a stoplight and as I acellerate it moves down to 51.4mpg... we're talking about 1/4 mile of acelleration -- and then I need to drive 5 or more miles at 60mpg to get it back to 51.8mpg. Doesn't seem right?

7 - 600-mile tanks... farthest on "normal" gas fill= 643miles

And ONE 735-miler!! (cheated, over-filled tank )