Yeah, the car thought I got 38.2 MPG. Trip odo doesn't tell you how much fuel you used, so I calculate the difference to be 0.311 gal. less in the car's "mind." Very Cmax-like.
And remember, I spent an inordinate amount of time idling on the first tank. It took a while to set up menus, and it's cold in January. Avg. speed was only 27.9 MPH despite an estimate of 25% highway. And I'm assuming this was 87E15 fuel.
The second tank is 91E0 fuel, and I'm trying to push the mode button twice to get into ECO mode. I'm at 933 miles now. and planning to take a trip this weekend, so I can report on a couple more tanks and some highway mileage.
When I filled, the miles-to-empty (MTE) display was only 450 miles, despite filling at 500 miles with 50 reserve remaining. It was easy to add the odo (at 500 miles) to the MTE (450) and get an estimate of odo at the next fill (950 miles). I've still got 177 MTE, so the sum is now 1110 miles. The car thinks it's getting 43.1. I expect highway more in the high 30's with ECO-cruise set to 71-72 MPH.
Have fun,
Frank