Can oil be substituted for butter?

It depends on what the oil was for. If it is a recipe, especially for baking, you can use butter as substitute for oil. It is not recommended to substitute butter to fry something because it tends to burn in a hot pan, you should use oil to fry.

Yes is can! Just don't use as much oil as butter. Butter is thicker than oil so don't make it too sloppy.