H23A1.

I have 87, 89, and 93 in my area. I've used 89 with no problems. Is 87 recommended? The guage cluster says Premium only.

 

It's not recomended, however I used to put 87 in my Gsr all the time, hit VTEC and everything, and nothing bad ever happened.

Now I just alternate between 93 and 89

 

Higher octane doesn't mean more performance, it just means there is less of a chance for your intake charge to pre-ignite and detonate during the compression stroke. As long as your compression level isn't super high, you can run lower octane with no ill effects.
If you decide to up your compression, then you should up your octane. My buddy uses low octane on his H23 and it drives fine.
-B

 

91+

 

"Premium" as defined by Honda is 91 octane. You can run 86 and 87 but the knock sensor will pull ignition timing making the engine have less power and hesitation problems too... It is up to you.

Pirate

 

Will low octane really cause hesitation problem? I can deal with retarded timing and less hp, but I don't want to damage my engine. Last time I put 87 in my car, it cranked longer than usual before it started (but I could be imagining things). Could low octane cause starting problems?
I think compression ratio on the H23 is 9.0:1, that doesn't seem so high. Aren't GS-R running 10.0:1? Is there another reason other than high compression to use high octane? I understand that high octane gas is use to prevent premature ignition (detonation), but is there any other reasons?

 

The H23A1 has 9.8:1 compression ratio.

I tried 87, and in my head, it seemed down on power. Maybe I was just imagining, but I dont know. 93 went back in, and in a few miles, seemed back up on power.