3 quick questions.

Kaldaien

Anything with a high compression ratio needs premium fuel. It doesn't have to be a performance car even, dinky little high fuel efficiency turbo equipped cars often require premium fuel despite doing 0-60 slower than a Nissan Altima.

Performance cars just have it doubly bad, they burn more of the stuff and it costs more. But the OP should have done things like factor the cost of fuel / non-rotatable tires on a Z into the initial pre-purchase evaluation. Rather than deciding after the fact that the car's too expensive to operate and cheaping out on fuel.