My previous car:
Perodua Myvi 2011 Lagi Best 1.3 Ezi Auto
Petrol Used : Petronas Ron95
Engine Oil Used : Perodua genuine oil Semi Synthetic 5W-30
Mileage : ~107,000km
Modification : K&N Drop-in air filter & full set hotbits catback exhaust system
Tire size : 175/65/14

Scenario 1 (Daily driving)
Fuel Consumption : 12.0 - 13.0 km/l
Driving Condition : 10% highway 90% city

Scenario 2 (Interstate driving on PLUS highway)
Fuel Consumption : 16 - 17km/l
Driving Condition : 90% highway 10% city

I noticed the trip computer on myvi lagi best is more optimistic and reads a better mileage compared to actual petrol used. Usually it reads 12.6km/l but actual is about 12km/l.