There is some debate as to whether carbohydrates or fats are the body's preferred fuel. However, the body will burn carbohydrates in the form of glucose before it burns fat.

Natural gas is a preferred fuel because it is plentiful, cheap, and burns cleanly.

CNG is the preferred fuel because it is cheap for the normal man and it is eco-friendly to nature etc.

CNG is the preferred fuel because it is cheap & even eco-friendly by nikhil 8-aooehs-shj-boy's

It is not preferred or recommended it is required or you will do damage to the engine. Premium fuel of 91 Octane is required and must be used.