Yes, it can be reset. The procedure is outlined on page 22 of your owner's manual:
AVERAGE FUEL XX.X MPG / (L/100km)
Average fuel economy displays your average fuel economy in miles/gallon
or liters/100 km.
If you calculate your average fuel economy by dividing miles traveled by
gallons of fuel used (liters of fuel used by 100 kilometers traveled), your
figure may be different than displayed for the following reasons:
• Your vehicle was not perfectly level during fill-up
• Differences in the automatic shut-off points on the fuel pumps at
service stations
• Variations in top-off procedure from one fill-up to another
• Rounding of the displayed values to the nearest 0.1 gallon (liter)
1. Drive the vehicle at least 5 miles (8 km) with the speed control
system engaged to display a stabilized average.
2. Record the highway fuel economy for future reference.
It is important to press the SELECT/RESET stem (press and hold for
two seconds in order to reset the function) after setting the speed
control to get accurate highway fuel economy readings.
-Rod