Rick - Rockman asked about a 5.6 litre V-8. You posted info about a 2.3 litre - not the same animal.

Rockman - I have a 126 car with the small motor and it calls for 91 Octane, so I suspect your big V-8 would need at least that much.

At sea level or close to it, premium is 93 octane - maybe 94 in some places.

I wouldn't dream of feeding the beast anything less than premium, whatever it's octane level is wherever you live.

Would you feed Wal-Mart Tuna Fish to Miss America?