Petrol is not a good in a time where people do not know of its properties. If we find petroleum on a distant planet, it won't be a good until we can figure a way to get it here or use it there. To explore this further, explore the concepts of use value and exchange value. The amount required vs. the amount available Air is free because there is plenty of it. If there isn't enough of a good to go around to all who want some, then the usage has to be economized.
Goods produced for trade are also Economic goods.
Also, Menger uses the term value to denote the property of goods that are economic goods. He would say that air, available freely, has no value. The term is inappropriate. This page is NOT sponsored by any bookseller. Comments come to me.