@asd123 My XLi (tank 50 litre) it does about 500-520 when the fule light comes which means 15 litres still in reserve. I am rougly getting 14 kms/litre in city and more than 17 km/litre on Motorway.
U need to check if the air cleaner/filter is ok. If it is dirty change it. I changed after 10,000 kms and now the odo is about 18K, but still it is going well.
RU spending too much idle time in traffic snarls, that could be another reaosn for low milage you are getting.
Also try another good fuel pump.
Another observation, I found PSO petrol better than Shell in terms of acceleration/pick and quantity.