Is it true that CNG is a better fuel for automobiles than petrol?

The given statement is true.

Petrol and diesel on burning produce black smoke with many poisonous gases which cause environmental pollution. whereas CNG (Compressed Natural Gas) burns almost without smoke also CNG does not produce any poisonous gases. Hence it does not cause air pollution. Also, the calorific value of CNG is greater than petrol and diesel. So CNG is a better alternative to petrol and diesel.