CNG can be used as fule or not and is it any bad effect of CNG

Are you asking if natural gas can be used in your car? Yes but you need to change the carburetor, gas tanks, lines and other items for your motor to use it. Most have a small gas tank in case your NG runs out. There are garages that specialize in the change over so it is done correctly. Gasoline leaves deposits in the motor and that is why the oil is dirty when it is changed. Natural gas does not, so after say 10,000 miles the oil will still look new and clean. Since there is nil contaminates, there is minimal wear on bearings, tings, valves and other internal components of the engine so it will wear less and lost longer.