Just filled up my first time with 544 miles on the odometer. Put 11.203 gallons in. That's 48.6 mpg. That's about 80% at 70mph, the rest at city speeds.
The computer told me the average was 44mpg so it was a bit pessimistic.
This weekend I'm on a road trip, driving 400 miles 100% highway the computer tells me 50+ mpg. I'm looking forward to filling up again and doing the math.