Bro, if you get Original Diesel Filter of Mitsubishi company which will cost you around 3k - 4k, it will last around 12k -15k
2ndly @mitsu_man is 110% correct if you want good average then you should go for Light weight rims and thin tire that is 235/75/15, otherwise it wont give you any average in local, as we all know how the traffic is in lahore so, take his advice and change it's tires and rims
Mine Gen II is giving 10-11 km/l with 4D56-TI (Turbo Intercooler)