I bought a 1969 Chevrolet Chevelle SS 396 recently and want to know if unleaded gas will harm my engine. Also, will using regular unleaded instead of high-octane unleaded hurt? I’d rather use the less ...

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Modern engines contain hundreds – nay – likely thousands of different parts. There are valves and springs, at least one camshaft, engines also have bearing inserts, an oil pump, numerous gaskets, ...