I owned both 2006 x corolla 1.5 auto and axio2007 1.5 corolla. Axio is Super cvt 7 gear automatic. It gives up to 30 percent more fuel economy than previous 4 speed auto gearbox. At 80 km speed it's RPM on Eco mode is only 1300 while on old x corolla it's 2000 which gives saving of 700 rpm which means fewer opening of injectors and less use of petrol. Cvt means no CNG but old 4 speed auto is no CNG king either as it gives jerky gear shifts and very very sluggish performance.
At current rates of CNG which is 80 and future increase of up to rs 10 it is not wise to use CNG any more.
Axio gives rs 7.25 per km on petrol with 100 percent performance
Old x corolla gives rs 6 per Km on CNG with 70 percent performance
Old x corolla gives rs 9 per km on petrol with less performance than axio.