Bro, thats realy awful mileage, it should be at least 15 on long rout, within city, u may have no idea cos of different types of trafic jams etc..
i use Le ponnGaurd air filter and oil filter, drive the car between 80~95kmhr, with ac it gives me almost 15+kmpl long route MASHA ALLAH.;
On next oil change, do following actions":
Flush your engine with gud flushing agent like STP.
Pour in the engine low viscosity oil, like 10w-30 or 10w-40.
Do change the air and oil filter.
Come home, and park your car.
Switch off the car, remove -ve terminalof battery. and let be remove for whole night.
Next day, reconnect it, start your car , run idle for 2min. Than have some drive.
1st 50 kms fuel consumption might be high, than it will improve.
Pray to ALLAH, it may do a trick for you.