My 2.2 DIC seems right on, I checked it with manual check for months after I bought my HHR this past spring. On the low side I average 32.5mpg and if I travel the speed limit 36-37mpg consistently.

 

My DIC is awesome!
I'll never, ever go without one again.
The DIC mpg reading is always within 1 mpg and usually within .5 mpg

About E85 -
I was at the stealership today and noticed considerable difference in est. MPG between E85 & real gas.
Over 100 miles difference per tankfull IMSMC

 

FYI mpg on my 2001 Corvette with 21,000 miles.