MPG is no longer being calculated

Are you sure you are not looking at your tank average, instead of your trip average? Your tank average will settle to a near-constant value as the tank gets nearer to empty.

 

Your picture shows Trip A. On your steering wheel you have a Trip switch which cycles between ODO, Trip A and Trip B. If you hold the Trip switch down for Trip A or Trip B it will zero that fuel economy setting - you would do this, say, only when you fill up for Trip A, and each morning for Trip B for your commute. So Trip A would give you your tank average, and Trip B your daily round trip average. Somehow you have set one or both of these.

 

I'm not sure the previous answer was clear.
When your display is showing the ODO.....your total miles.....then the MPG figure beside that gets reset every time the engine is turned off.
The separate figure for trip A and trip B gets reset along with the trip mileage.
I use trip A for my "tank" mileage and B for long term average.......except when the wife fills up and resets EVERYTHING.

 

funny, i think another c owner posted the same thing awhile back.

 

be careful holding down Trip if itz just the ODO odometer. it will jump to kph instead of miles per hour. to avoid that mistake is why i usually leave it on trip B now.
if you do go to kph, just go back to ODO and hold it down again to go back to miles per hour. no need to panic.

 

I use Trip A for each tank and Trip B for each oil change.