on a healthy engine, by that I mean good sealing rings and tight valve guides with good seals, a lean carb will burn through a rich fouled plug like 123. but to make it simple when you lack experience, new plugs give a neutral basis to start from. it does make it easier.
if you start to see aluminum specks on a white plug insulator, you are way lean and if the exhaust is smoky and stinks on a dark colored plug insulator, you are way rich.
