I am wondering if anyone can help with some octane recommendations. I have a 99 Civic SI capable of 405 whp at 18 psi, but want to run at a max of 10 psi for reliability. Do I need to run higher than 93 octane to avoid too much detonation? And do very high boost set ups run 100+ octane? The car I have was tuned on 93 octane, but I am not sure if that was at max boost. I am lead to believe that 18 psi requires some very high octane gas...any advice is appreciated.

 

at 10psi 93 octane is perfectly safe granted you have a good tune. At 18psi you need to make sure you have a very good tune if youre gonna run 93 octane. just to be safe I'd run the higher octane over 15 pounds

 

How do you not know what octane gas you had in your own car when it was tuned? If it was tuned to make 405whp on 93, then drive it on 93.