Well i have MashALLAH amazing pick and on average gas quality the car can sustain 120 km/hr on motorway with AC
And on Good CNG like from Bhera Chan CNG i can even maintain 140 after salt range though you know we are gaining in terms of altitude .
The trick behind this average is combination of few things.
1) Always get gas filled from 1 cng station while in local and it has amzing quality.During my local usage i have only tried 5 cng stations PSO of jhanda , Al Basit and Shell on swan bridge road , TM Cng on isd highway.95% of my local mileage is based on these cng stations.
2) In Local as my daily travel is around 65-80 km so it becomes long route
3) Regular maintenance after 5000 km
4) I dunt knw wether it matters or not but i start the car on petrol every morning till the temperature gauge is at quarter and i drive 15-20 km on petrol after ever 2-3 cylinders used on CNG.