I have visited this site a number of times since getting my '08TCH on Jan.14.
I appreciate the FAQ post and all of the questions shared by all of us new owners.
The one thing I still would like to find is the definitive explanation, ideally from Toyota, concerning how to interpret ECO Drive, and all of the displays in detail.
Have I missed something obvious? The manual does not go into the specifics of any of the displays and I wonder what they all mean.

 

I agree that the "Manual" leave a lot to be desired.

A suggestion would be to get familiar with the "SEARCH" function at the top of this website.

Now, as far as your question:

The ECO Drive indication shows the average mpg since you started the car. As you can see, it is a stair step display and is updated every 10 seconds. Also, the outside ring of the speedometer and MPG guages change luminosity with the ECO Drive stair step. the stair steps are:
Level 0 -- 00 -> 25 mpg -- Meter Brightness -- OFF
Level 1 -- 26 -> ~ 30 mpg -- Meter Brightness -- Subtle
Level 2 -- 31 -> ~ 35 mpg -- Meter Brightness -- Medium
Level 3 -- 36 -> Infinity -- Meter Brightness -- Full Intensity
When you turn off the the car, the ECO Drive display (MFD) retains the ECO display for 3 more seconds. And if you're a good little boy or girl, it displays "EXCELLENT" if your average was 36 MPG or more. Your spouse's (or S.O.) consistent failure to attain "EXCELLENT" is definitely grounds for divorce. (Or at least take their FOB away from them.)

If you have NAV, you can see a more precise indication of your fuel economy.

I hope this answers you question about the stupid display.

 

Thanks John! At least now I know the relative meanings of the shading and the graph. I have gotten the "excellent" reading a couple of times and I obviously knew what to strive for but it is good to know specifically what I did to achieve it!
I don't intend to become obsessed with MPG (read-hypermiler I ain't) but it is good to know that very good mileage is a given and excellent mileage can be a goal.