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Highest I've seen was 117 octane at 7.95 a gallon, and that was at infineon race way, used to be sears point.
"Race gas" won't don anything for your car because our engines are only 9.5:1 for you non vtec people adn 9.9:1 for vtec. Now the reason why some of you say you get gains or your car drives better with higher fuel could be because the "87" octane is not really 87 or it's a mix with ethanol and other ****. so when you put in 89, you're really getting like 87... anyway, the octance number just means how resistant the fuel is to spontaneous ignition caused from compression, when you compress something it heats up, therefor, the more compression, the more resistant it has to be so it doesn't fire on the upstroke, this is known as knocking. If you put 87 octane in a engine that needs 91 then it will destroy it. while putting 91 octane or higher when your car doesn't need it does nothing. LASTLY, those of you who "feel" results, typically you have to run through a couple of tanks of gas for your ecu to even realize that it has different stuff in it.

-Mark Nealey

 
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IF you go into unuion 76 gas stations you can get 117...35 bucks for 5 gallons.

IT is cjust wasted money.

 
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in japan they sell like 115 at gas stations lol

i filled up my car a minute ago with 89 and i CAN TELL a good difference than when im on 87 or 93. everytime i fill up my car accelerates faster, for sure. i love it. when i get to about a half tank it goes back to normal though.

 
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Ok, I've been running on 94 forever and have noticed signigficant improvements over 87. However, since the popular opinion here is 89 is best than here is what Imma gonna do. My car whould be bone dry by the time I leave work tomorrow so I'm gonna get a tank of 89 before the meet tomorrow night.....I'll let y'all know what I find.

 
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i gotta try high octane to see if there is a difference. i have always used the cheap stuff, i think the car runs great.

 
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I tried 100 octane in my 900RR, and couldn't tell the difference.

 
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I was convinced anything higher than 87 is worthless after trying 91 once I was using 89 for a while. There was no difference.

On an older thread, I recall someone once tried racing fuel in their Civic - and it had no type of boost or parts on it that required a higher octane. I remember someone saying that the car WAS faster with racing fuel, but another person (I think it was Mohawkboom) it will harm the engine in the long run because simply the engine just isn't designed for it. I think it could cause pre-detonation or something?

It seems like from the people here that whatever octane you can get at a regular pump isn't going to make such a huge difference. And I'm sure if any one of you guys who are running 89 or 91 without any mods that require a higher octane - if you guys went back to 87 now, you wouldn't notice a negative difference at all and realize just how pointless it is to go higher.

 
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Just to throw my .02 into the often talked about subject of octane levels and performance, it is a misconception that running higher octane than what the manufacturer recommends will not increase performance, because it will, ON CERTAIN CARS!!! For example, a Honda engineer has already admitted, and it has been proven, that the J30 on the new 7th gen Accord V6s gains about 10hp from running high octane vs. 87. However, the J30 in the 6th gen Accords, which was quite a bit different despite being the same displacement, actually LOST power with high octane. This was proven in a test done in Car & Driver or some such mag. So, the point is, some cars can benefit from using high octane, some cars HAVE to run 91 or better, like supercharged or turbo'd cars, but 95% of newer cars out there don't gain jack from anything higher than 87. Unless someone has dynos of a bone stock D17 Civic with and without high octane that show an increase with it, I'm sticking with 87.

 
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Umm seen 100 octane fuel around here but thats about it they offer 92 at the pumps here in Premium.

Nick

 
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US an Ca made Civics are tuned for 86 octane. If you run into problems running regular grade gas here, then you have engine problems that need to be remedied, and not just masked using a higher octane. Also, using too high an octane can cause problems over the long run.

On a side note, and if I remember correctly, countries in Europe have octane grades starting around 100. Of course, the cars sold there are tuned for that grade of gasoline.