Octane rating scale, gasoline

An octane rating scale was devised for fuels to quantify their knock resistance. Further research led to cataloguing the antiknock qualities of the myriad individual hydrocarbon species found in gasoline. 

The other large-scale ethanol user is the USA, where ethanol has been used to increase the octane rating of gasoline, to decrease carbon monoxide emissions, and, more recently, to replace MTBE (methyl tert-butyl ether) in reformulated gasoline. Ethanol production in the USA grew from about 0.6 billion liters in 1980 to... 

Gasolines are usually rated according to the octane number, a measure of their tendency to cause knocking. On this scale, a branched Cg compound (2,2,4-trimethylpentane, or isooctane) has been arbitrarily assigned an octane number of 100, and that of n-heptane, a straight-chain compound, is zero. The higher the octane number of the hydrocarbon, the bet-... 

The octane number is a scale used to rate gasoline. The octane number of the following compound, called iso-octane, is 100. Classify the carbon atoms of this compound. 

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