[PandaMoOo]

Someday someone asked me what octane gas I put in my motorcycle, and I simply said "91" at that moment I realized I had no support for the idea of paying 20 - 30 cents more per gallon except others have told me so! I did a little research on the internet and found not only does higher octane gas provide no power increase, but that it can actually put extra gunk in your engine over time!

What Octane Rating is:
To keep things simple, Octane Rating is the rate at which gasoline reduces compression explosion. See, when your engine squirts a little gas in a cylinder, compresses it, and then it a spark goes off. If your octane rating is too low, the heat generated from the compression may ignite the gas prematurely and cause a "knocking" or "pinging" which is damaging to your engine.

To combat knocking and pinging, gas manufactures have made some gases that don't convert from liquid to vapor form as fast, thus helping car owners not damage their engines.

Higher Octane Gas has more detergents though!:
Yes it does, but thats also because higher octane gas leaves more crap in your engine. With higher octane gases, not all the gas vaporizes before the spark, leaving some carbon atoms in your engine. A lot of gas dealers put EXTRA detergent in higher octane gases so people don't actually damage their engine from paying more. All gasolines have to meet a reasonable federal standard for detergents, you can also pay about $6 and get a carbon cleaner from an auto store to clean your engine.

Exceptions:
The only real exception is if your engine is DESIGNED for high compression. A lot of more expensive cars have more powerful engines that use higher compression to help achieve that power. If they don't get the higher octane gas, they may get "knocking or pinging" which will decrease performance and damage their engine. So... read your manual if you got a high performance vehicle.

For all other cars, they're designed for 87' gas.

In fact, the higher octane gases have been proven to be lower performance because of two factors:
a) Less gas is vaporized before the spark hits.
b) More detergents = less hydrocarbons = less Energy.

So do yourself, and your car a favor, switch over to lower octane gas and stay away from bullshit gasoline companies trying to make you believe octane is related to power, it's not.

If you don't believe me, just search the internet for "higher octane gas" and you'll find hundreds of references I read, or if you don't care about $100 or more a year, I don't care about your money. I'm just trying to help the ignorant learn, because I too once didn't know about this.

(This is the first of a many threads I plan on creating debunking socially excepted norms, I recommend all users at least look for them, and read them and make their own judgements.... It would be cool if other's did the same!)

Sources:
http://www.personal.psu.edu/users/b/j/bjy116/conversion.htm
http://autorepair.about.com/library/weekly/aa060504a.htm
http://www.straightdope.com/columns/041008.html