Originally Posted by
Fivefingerdeathpunch
What you feel and what is actually happening are two different things.
If you did back to back dyno sessions with pump 87 and pump 93, the 93 octane is going to produce stronger numbers. You beat on a engine running 87 octane it will catch up to you, not that it's going to harm it more so in what the computer is going to see and do because of running lower octane fuels.
87 octane has less resistances to knock compared to 93 octane. You flog the piss of out it on 87 and it will start to show knock as cylinder temps continue to rise. The computer can seamlessly pull timing away to keep things safe and doing so it's robbing some horsepower and torque. We aren't talking 50hp here but probably 10-20hp and that is not something you are going to notice in the butt dyno because there are so many other variables going on.
If you want it to run at it's best with the potential to have it's most power, you'd need to run premium fuel. Or if you ask me, at least 89 octane. I've tuned many LS based V8 engines and 87 is just terrible for making good consistent horsepower with minimal to no spark knock.