Doesn't seem to be the case. If people really wanted to save fuel, they wouldn't leave their cars idling with A/C on, and drive at or below the speed limit while maintaining traffic buffers (in other words not tailgating).
Anyways, Liana and Alto came factory installed with proper CNG kits. Unless the OP has a GLI ecotec, or has a professionally installed lambda kit, his engine will give problems before long. Cheap CNG kits are not meant to work with electronic throttles, especially when they are combined with VVTi systems.