The guy said he mostly use 7th avenue, so no brakes no traffic signals and max speed 70 km/h
I think Liana can give this mileage on 60L cylinder if:
about 9 Kg + CNG is filled on 220 bar pressure,
without AC,
single person load,
CNG main value opened in its minimum compromising the acceleration,
Stock tyres (165 wide i think)
running on 70 KM/Hr speed
and WELL TUNED.
My Friend has Liana LXI and it gives upto 190 km/60L cylinder (daily travel from Korang town to I-8 on Islamabad highway)