Cultus 2015 Average issue

[Shaffang]

I am having Cultus 2015 (old shape)(Note:Its only on Petrol) but the fuel average it's giving is around 8.5-9.5km/litre....My Mechanic has already cleaned the throttle body and also applied WD-40 plus I also made decrease the rpm to 800-900 but still the average hasn't increased much.
Now I went to another mechanic he said the car is fine just run it on hi-octane and petrol with a 50:50 ratio and its average will increase....So should I try using Hi-octane or not ? And if you have any other suggestions then do comment.

[dayrider]

No need for high octane. Whats the total mileage of the car? get the MAF checked, along with the O2 sensor. Some sensor is malfunctioning, this car does 13 kml local

[Shaffang]

The totale mileage is approx 35,000 km

[dayrider]

How do you calculate the average and do you drive with a heavy foot?

[Shaffang]

I calculate the average by dividing the daily petrol intake by kilometers driven....My car is actually driven by a driver for in Uber so daily he does approx 180-200kms

[dayrider]

Uber has a lot of stationary fuel consumption. And are you sure he puts in fuel of all the money you give to him? Why not on a day off. You take it out and calculate the average yourself?
If not, how is the performance otherwise, anything outside the ordinary in driving?

[Shaffang]

Yeah I agree to the stationary fuel consumption...Daily I fill up the fuel in the car so I know how much fuel is in the tank....well in this work a day off is like a day of loss but still the druver takes a day off in a week or so...yes I take the daily travelled kms divuded by the fuel added in litres....The performance of the car is great bcuz cultus is the most suitable car for this work bcuz this car easy to maintain and works fine in rough terrains

[dayrider]

Does the car have accidental history? Does your driver drive with a light foot? Does the car have a history, are you sure it's only 35k driven? Post a picture of the engine bay please. If that is not an issue