The name "octane" comes from the following fact: When you take crude oil and "crack" it in a refinery, you end up getting hydrocarbon chains of different lengths. These different chain lengths can then be separated from each other and blended to form different fuels. For example, you may have heard of methane, propane and butane. All three of them are hydrocarbons. Methane has just a single carbon atom. Propane has three carbon atoms chained together. Butane has four carbon atoms chained together. Pentane has five, hexane has six, heptane has seven and octane has eight carbons chained together.

It turns out that heptane handles compression very poorly. Compress it just a little and it ignites spontaneously. Octane handles compression very well -- you can compress it a lot and nothing happens. Eighty-seven-octane gasoline is gasoline that contains 87-percent octane and 13-percent heptane (or some other combination of fuels that has the same performance of the 87/13 combination of octane/heptane). It spontaneously ignites at a given compression level, and can only be used in engines that do not exceed that compression ratio.


ok so if 87 octanne is 87 percent octane and 13 percent hectane or whatever then what about what the japs use?? its like 103 and up octane... are u saying its 103% cause that dont make sence can u clear it up a bit

 

hm howstuffworks says you cant have more than 100 octane...
perhaps it is proportional by adding a more powerful by density substance?
like... i dunno im not sure but maybe there are stuff that is more combustable that they put in there to boost power.... and teh number is like...
okay so if you have 100 octane and you made a mixture that made the gas a lil more powerful like... you had to tell the consumer that it was more powerful so how do you do that?
you tell them that gas is 100 octane and 105 octane is 5 percent more powerful than gas... maybe
just a thought ... im not sure so dont quote me

 

Great info! Thank you