Easily get? Perodua famous for overstating by multiple times their FC. New Alza for instance claim 22 km/l, even with purely highway drive and no jam from KL to JB I was only hitting 14 km/l. Fuelly.com shows the old Axia (the best FC Perodua car so far) roughly 15 km/l with mixed driving and 17+ km/l for highway driving, no way the new one easily gets 20 km/l.

Nobody is talking about drag racing here or comparing Accords to Myvis.
I can see a presumptuous trait going on here.

I have owned both Axia 1.0 and a Myvi 1.5 ICON. the FC between both are similar at best and
the Myvi is slightly better some times, depending on payload, route, traffic conditions and way of driving.
If one can afford it, get a car with a larger engine. Maybe its just me as I am the type of driver who is
not concerned with fuel consumption at all.

Regarding the term "no replacement for displacement", lets just agree to disagree here.
We are all entitled to our own opinions for better or for worse.

No point debating about this for no mutual gain as this could escalate into a nasty argument.
I will consider this topic closed.

Have a nice day, bro.

This 'hardcore one' is still below 19 km/l, and like anything else on fuelly you need to look at the data distribution for a good idea of how the real FC is. Can clearly see two peaks as I have mentioned, one at 15.5/16 and one at 17.5. Most cars have this pattern, where the lower peak corresponds to more mixed mode driving (city + highway) and the higher peak corresponds to primarily highway driving. Compare, for example, the Viva which has the same pattern with peaks at 13.5 km/l and roughly 16 km/l.

The reason to look at the distribution is because, as you said, 'was this real?'. Single outlier results, chance to be fake (or at least misttyped) is higher, that's why we look at the averages.

I have never done any engineered study but just based on my normal routine on highway to work observed over a period of time.

I owned an Axia 1L and been using it for 5 years. It is an auto. Could not remember the stated spec but after refueling the car on the way to work. Reset the car fc meter to zero I can get about 20km/L. Tried that on numerous occasion. Roughly the same results. I think the spec called for 21.x km/L. Speed around 80km/h or 100km/h I see no difference. On way back the traffic was more heavy and the average dropped to about 15~16km/L. It would improved back on the morning to office.

Now I owned a MyVi 1.5L auto. Similar test I can get around 21km/L but I thing I observed was that the MyVi improved its fc average much faster than Axia. My observation was that on highway the MyVi can average about 18km/L and Axia about 15km/L on routine to and fro to office over easy and and heavy traffic. In city driving, the MyVi gets around 15~16km/L and Axia was around 12~13km/L.

All these were based on normal routine route on highway and also in city.