Not an apples to apples comparison. I don't know when the calculated Octane Rating changed, but in the muscle car heydays, octane was calculated as RON. Our fuels now are calculated by the anti-knock index which is (RON+MON)/2. Fuel octane measured with RON alone will be higher "Octane" than fuel measured as (R+M)/2. Its the same situation we see when talking to the Aussies for instance. Their "98 Octane" fuels are close to our 93 octane fuels. It's just a difference in how the octane rating is calculated.
What IS a known issue is the existence of anti-knock and lubricative agents such as tetra-ethyl lead. Many vintage cars (including but not limited to Pontiac) did not use hardened valve seats. There wasn't as much of a need because the TEL cooled and lubricated the seats and kept them from wearing.
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-Jason
1969 Pontiac Firebird
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