Hey, maybe I can share some tips or encounters for you or others here...
AVG counter should be good enough, but it must be reset depending on what you want to measure
Ie. I pump full tank, reset it, drive from PJ to Melaka, reach destination and read the AVG meter, I got 23.Xkm/l for that journey.
This was a very special case! It was raining moderately all the way, traffic was really good and everyone on the road kept steady at about 7 to 12 cars distance.
The speed was about 60-95km/h. There were many times at downhill slopes on the highway, I could just let go of the pedal and let the car glide by itself and enter fuel cut. When reach Melaka town i was impressed.
(You can monitor fuel cut, it happens when you are above 55km/h or so and let go throttle completely. The real time meter goes to 99.9km/l, if you are on good road surface and have a good ear, you can literally hear the fuel injectors stop ticking)
I also find that for moderate slopes (not very steep / Genting kind) or even generally, the car is most efficient around 90km/h
Ie. To maintain 90km/h up a slight slope, the real-time meter is about 15 -18km/l
Ie. To maintain 70km/h up a slight slope, the real-time meter is about 11 -14km/l
Where I stay and work no need say lah (PJ area), so many slope roads here and there and so many traffic lights for bloody short distances, max is about 13km/l. Previously driving myvi around 10km/l... pretty ok lah.
Nevertheless I also observed the car is most efficient after it has entered 3rd gear. At 3rd, the real time km/l is above 10 already at light throttle...
I believe the earliest shift to 3rd happens at about 35km/h. Also, once u are in 3rd and 4th, the gearbox applies the lock-up clutch at light and moderate throttle for best efficiency.
Hmm i think lastly try not to linger too long below 30km/h, last time i thought if I accelerate sloooowly below this speed it will give good consumption, nope. It's actually saves more if can reach 40km/h or above in reasonable time. Don't floor it or be aggressive but don't linger below it too long either. If you watch the real time fuel meter at the lower speeds, you will know what i mean

At this speed even at light throttle, no car out there can give good figures (except hybrids

)
The real time meter really helps to have a glance on how much fuel is being used at that moment and situation, but don't get too distracted and stay safe! Cheers
Nice write up and sharing.
In all my cars, I prefer to get it up to cruising speed quickly. The sooner you reach 90km/h - 110km/h, the sooner you're in the optimum range. That's when consumption is at its best in long distance driving.
After that, maintain momentum and anticipate conditions ahead of you.
As for city, there's not much you can do apart from being smooth and anticipating traffic. Eco idle really helps in long traffic light waits. I find myself in 10mins of traffic lights for every 50mins of driving.
My mixed average after 1yr of driving the bezza is 18.5km/l at best, 16km/l at least.