city does have a bit knocking issue but its not that worst also pick wise i think only 2nd gear lags that too between 1000-2000 rpm after that its all good,,, solution to knocking is same what u did 30% hi-octane, and use 1st gear up to 20km/h and 2nd up to 40km/h at least , if u r using normal patrol if it still causes prob then there has to be some issue,,, my city did 9km/l city and 12-13 km/l on highway initially but now around 3.5k driven its improving on highway up to 15.5-16.5 km/l and in city its 12.5 km/l and the ac is always on,,,, many ppl say it takes from 5k to 8k on the odo meter for it to reach a good millage,,, till then u have to bare, i think city's ecu doesnt provide mush fule at low rpm and so it has less torque at those rpm where as above 2500 rpm its a beast, better then any other 1300cc