Using Gas Octane below the requirement.

[why?]

Originally Posted by Irace86.2.0

Lower octanes worked better with carbureted engines back in the days before fuel injection could correct for air density. It would be incorrect to say they work better today. It would be more accurate to say that at a given RPM in a given gear, at altitude versus sea level, there is less air density, so there is less need for as high as octane.

Now, consider the need to do a given workload. If a car was going to go up a 15% grade at 65mph at altitude versus sea level, what would need to happen? Since there is less air density the vehicle would need to increase its efforts, possibly reving much higher. In the case of a turbocharged engine, the same psi could be realised but the turbo would have to work much harder to pull the air into the motor. This is like trying to run on sand versus pavement. In my eyes, more work means more heat, and more heat for the same workload or work output means there is a greater likelihood of knock.

I could be wrong, but that is how I see it.

you totally overanalyzed what i said. Nothing you said is wrong. There is a reason high altitude areas have lower octane gas available than sea level areas.