Assuming that you completely emptied the 30L fuel tank, you are averaging just over 26 km/l. In my opinion, it is totally possible if the car is in the absolute best condition, using some really advanced hypermiling techniques.
I myself am expecting 500+ km (right now 320) from my current Cultus VXR tank (leaks oil, direct fan, 20w-50, at least 4 cold starts a day, rush hour traffic; starter motor slips when hot, so I can't shut it off once the engine is warm ).
If you are not using advanced hypermiling techniques in a perfect car, you should recheck your fuel economy measurement method.