I decided to quest for 700 miles for a tank (and by the way, it's gonna be close, I have about 1/4 tank left and am at 565 miles).

Now my lifetime average MPG is around 43mpg in my 05 HCH. I swear I have no idea why it's so "low", I do all the special tricks and a LOT of the time I'm able to cruise at 70+ mpg.

Anyway, I decided to try for 700 miles (I do have two 600 mile tanks). To do this, I completely filled my tank, I mean all the way up to the filler hole (ya, I know, cheating).

The first 100 miles I was at 54mpg average. At the 200 mile mark, total average was down to 49.9. By the 350 mile mark... going back-and-forth between 47.3 and 46.9. It has stayed there until 550 (where I am now).

When I saw it going down I decided to reset the other Trip meter... for the last 300 miles (the 200-500 mile mark on the main trip meter) I've gotten only 42mpg.

I promise my driving habits have not changed during this tank. I've driven on very similar roads, the ambient temperature is very similar (60-70 degrees), etc.

I've also found this to happen in the past.. the mileage starts at the beginning of the tank SO high.. then by the end of the tank I end up averaging 42-44mpg.

What is up with that?

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

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