Ive averaged slightly more than 14 Km/litre with of and on AC (about 60percent of the time) short trips (max 10 Kms) and in terrible Karachi traffic, although on better roads and I think its quite an achievement, never seen any mileage like that. Just keep the good driving tips in mind...
P.S:, get the throtle body (below air intake) throughly cleaned by a good mechanic, as these vitz are used, and see the increase in mileage by about 2 Km per litre
Also, use a mixture of HOBC and Supreme fuesl, because we are misled on pakistan about the ron figures of petrol, the extra mileage you get will offset cost of HOBC...
Regards
Deloy