I live in Kansas, and out here, the octane rating for premium fuel is 91. now, i know this is what the book recomends for the engine, but in st. louis their premium fuels are set at a 93 octane rating. why is a 2 digit difference in octane, making such a difference in how my engine runs. are there additives that are safe to use to boost octane, without damaging the engine or shortening its life.

 

Not sure why there is a difference. Are you going to use the 93 all the time? or just once in awhile when you go there? I don't think that it would really hurt it. I have read in tech areas for the 05+ and when people get CAI's and tunes, depending on where they live, the tune will come with either a 91 tune or 93 tune. I don't think it will damage anything. But if you are going to use 93 all the time, maybe you can get it tuned for optimal performance.

In my short stint living in VA, they had 93 as well, when I moved back to CA it was 92(that is what it was before I left to VA as well), then a year later it went to 91. The bike I had ran premium. It didn't seem to really effect anythng, but that was carbed and not EFI.