Thank you for creating this thread. We should all include the source of our data, so folks know how good the data is.
This was posted on PriusChat and linked to by MetroMPG.com.
Also, when Wayne Gerdes reviews a car, he does an mpg vs mph test on it.
Edit: Here's his data on the Honda CR-Z, 6mt, with cruise control and Eco Mode engaged. Ambient 66-68°F.
Originally Posted by Wayne Gerdes
* 45 mph - 58 mpg
* 50 mph - 53 mpg
* 55 mph - 49 mpg
* 60 mph - 46 mpg
* 65 mph - 43 mpg
* 70 mph - 38 mpg