where are you from ? take the vehicle on highway and drive the speed upto 70Km'H then release the throttle pedal and gently press it so only you can maintain your current speed then reset the trip meter eco meter and drive steadily for 20 to 30 km's you will stabilize the onboard eco meter.
remember accelerate gently if you loose the speed else you will not be able to reach peak economy of onboard ecu monitor good luck.