1958 Cadillac what octane of gas?
Cadillac 1958 with the compression ratio of 10.25:1 should not run on gas below 98 octane.
Probably, yes. Gasoline comes with different octane ratings because some engines require a higher octane to prevent pre-ignition ("pinging" under acceleration or on hills). Check your owner's manual. Also, you can experiment with lower-octane (and therefore less expensive) gasoline. If you do not experience pinging with 87 octane gas, then that is all you need. (Technically, a higher-octane gas burns slower than lesser-octane gas, but that is beyond the scope of this question.)
Use exactly what your owner's manual states. If it says 89 or 91 octane then do not use 87 octane. Using a lower octane that required may cause pre-detonation or what is commonly called (Pinging). Pinging may be harmful and may cause engine damage. Bottom line is to use no lower or higher octane fuel that the engine was designed to run on. Using a lower octane can cause engine damage, and using a higher…