I've reset all mine every fillup. There seems to be so many variables that can influence the average reading.
I was responding on another poat regarding the hood deflector I installed about 3 weeks ago.
At that point the discussion was the shield may increase gas consumption. At the time I agreed, just because of logic.
At the time I believe I said it was 10.8 ltr/100 Km. But daily as I commute back and forth to work it would drop by .1.
Now the variables all kick in. Since the install, the consumption has been improving but then so has the weather and the break-in milage / Km's.
With the morning's being above freezing you don't get the warning of possible ice.
I think that is part of the defrost kicking in at a given temp / humidity, thusly turning the AC on.
Less warmup time for the choke as well.
As of last night all city driving, it was at 10.0 lt/100kms. The Nox is at 4,100 Kms. now. All this in ECO mode.