Fuel Consumption is 5km/liter

[innova2013]

Na observe ko after changing my oil from 20w50 to 10w40 and also from bosch platinum spark plugs to OEM spark plugs, fuel consumption ko naging 5km/liter na lang. bago din naman ang air filter. car is 1997 corolla 1.6 gli with 123k mileage. Ano kaya ang problem?

kung humina hatak ng makina sir, possible nabawasan compression dahil sa mas manipis na oil na ginamit kaya lumakas fuel consumption.