Wilbur I did a little research and the 8-85 has a idle octane rating of around 105 and a usable octane rating near 120. So you can run extremely high compression upwards of 16:1. It retards predetonation so you can run quite a lot of timing advance. I have never messed with it I just ride atvs with people that build motors for their atvs that run on it.