as far as i know , any new car does around 8 or 9 km/l for the first 5000km , and then after the 5000km tuning , checkup , oil change etx , it does what its supposed to do .. a city (2009 onwards , manual) does 13 or 14km/l (depends on how u drive , 13 or 14km/l is achieved when rpm mostly kept below 3200rpm)
also , installing bigger tyres will make the car heavier and so fuel eff drops .. also tht u cant really measure fuel consumption when u've deviated from stock size , as the 195/65R15 tyre's diameter will be much greater , so the odo might say 100km while in reality u may had covered 110km .. even the speedometer showing 100kmh , u may actually be travelin like 103kmh ... so i wud recommend to use 185/60 or 185/65 if u wanna avoid 175/65 stock... exact calculations here Car Bibles : The Wheel and Tyre Bible Page 1 of 4
.... peace