You can't buy gas from a normal station for either of those compression ratios today. You barely could - ever.
Although each engine may be a little different an 11:1 ratio nominally requires 104 research octane number (RON = R) fuel. When measured by the motor method (MON = M) the octane of that fuel is lower at around 94. The pump at the corner station is marked with (R+M)/2 meaning you would need to find a pump selling 99 octane gas - good luck. The cans of 'lead' you add aren't all that effective and I doubt you can add enough of them to make up the difference. When they talk about increasing octane by so many 'points' they often mean 0.1 octane, NOT 1.0 octane points. Racing gas and/or avgas come to mind. You need a good job to pay for either but they will still likely be cheaper than the cans of additive.
I re-built my engine at 9.5:1 for just that reason. In the 60s Ford called that a 'regular fueled engine' as opposed to the premium fueled 10:1's or the super-premium 10.5:1's. My 9.5:1 will need 93 octane at sea level but at least that is still available but its now called 'premium'. I mention sea level since at higher elevations the octane requirement is lower. Living at more than a mile above sea level my 9.5:1 can burn regular which up here is only 86 pump octane. No, its not any less expensive, its just lower octane.
11:1 has a typical thermal efficiency of 34% while a 9.5:1 is only 32.5%. To me that less than 5% loss in HP with the lower compression would seem worthwhile today since it allows cars to be driven on the road without needing to own a major bank.
Although each engine may be a little different an 11:1 ratio nominally requires 104 research octane number (RON = R) fuel. When measured by the motor method (MON = M) the octane of that fuel is lower at around 94. The pump at the corner station is marked with (R+M)/2 meaning you would need to find a pump selling 99 octane gas - good luck. The cans of 'lead' you add aren't all that effective and I doubt you can add enough of them to make up the difference. When they talk about increasing octane by so many 'points' they often mean 0.1 octane, NOT 1.0 octane points. Racing gas and/or avgas come to mind. You need a good job to pay for either but they will still likely be cheaper than the cans of additive.
I re-built my engine at 9.5:1 for just that reason. In the 60s Ford called that a 'regular fueled engine' as opposed to the premium fueled 10:1's or the super-premium 10.5:1's. My 9.5:1 will need 93 octane at sea level but at least that is still available but its now called 'premium'. I mention sea level since at higher elevations the octane requirement is lower. Living at more than a mile above sea level my 9.5:1 can burn regular which up here is only 86 pump octane. No, its not any less expensive, its just lower octane.
11:1 has a typical thermal efficiency of 34% while a 9.5:1 is only 32.5%. To me that less than 5% loss in HP with the lower compression would seem worthwhile today since it allows cars to be driven on the road without needing to own a major bank.
