This helps me from 8.5 9km average to 11.5 to 12km on average... I have tried everything possible.
Solution: Engine flush through liquid moly and add 10w40 or 10w30 liqui moly oil and also add cera tec go to liquid moly certified branch in Lahore you can google it or also you can find on their website.
Now most important part no matter what do not accelerate hard, no push slowly take it to 45 or 48km/hr speed then you can accelerate hard up to 70 or 80km/hr but try to accelerate in a way that your eco mode stays on... it looks hard in the start but after some time you will see the result.
One more thing: go to average and hold the button for 5 to 10 sec it will show u the setting to turn on or off the eco mode turn it off first and then hold it for 5 to 10 sec it will take you back do the same and turn it on it will refresh your system in the case is there any problem.
for most Vitz, we use big tires it's fine but make sure to use average profiles and dont go so big or so low. Thank me for your prayers.