I drove my car until no petrol and luckily it happened a few second after I enter my apartment premises.

Finally tested in a unexpected safe manner.

fuel indicator show @ 345KM
fuel indicator blink @ 383KM
engine die @ 431.2KM

-went to Shell to get 4 liter petrol.
-drove about 4KM to Mobil station and refilled.
-refill gun auto stop at 39.084 liter
-futher refill until 42.691 full, almost spill out.

so my humble conclusion, 50 liter tank(lil bit doubt now) but runnable capacity is 46liter-47liter.

p/s: this trip is heavy footed, else normally indicator show at approximately between 400KM-420KM