Need Help With Fuel Consumption

hi i just bought a second hand spark and wanted to know how to reduce fuel consumption . My current fuel consumption is roughly 30km/l or less(thats bad for a spark right ?) . Normally riding on expressway 90-120km/h just to get to work and home . 2 days i will travel a total of roughly 88-90+km and having to top up 3-3.5l of petrol .
FZ block
FZ piston ring
FZ piston
sp carb
CDI BRT
Aftermarket pipe .
fuel used spc 98
idle speed at 1.5rpm
Bought a spark hoping for it to be fuel saving but...

Need Help With Fuel Consumption

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