Have a new Buick, but imagine it's similar for all new GM cars.
Re the display that shows the approx. mpg:
There is a reset button that one can push.
Is the mpg computed from the push of the button, continuously, irrespective
of how long
the trip is ?
e.g., the mpg is a "true" average for the entire trip.
Or, does it continuously re-compute the average mpg, perhaps every few
seconds or so,
and updates accordingly (for that few second period) ?