As someone said - it's printed on the inside of the fuel flap. The idea of "not knowing" a cars previous means you'll not bother "incase" is ridiculous.
If you're going to use "normal" to save a few pennies here and there after buying a Z with its high tax, insurance, and maintenance costs - then saving pennies on fuel is, frankly, nuts. You bought the wrong car for your budget.
Buy a cheap-to-run and maintain daily instead. So I'd definitely recommend using super and enjoy the point of owning the car