the dreaded octane question

[andrewvickery1]

I have seen many posts about octane and everyone recommends reg 87 but I found this on my wing.
Now I am totally confused because it says 91
Please help

[tfdeputydawg]

According to the 'Bosch Handbook,' the two methods of measuring knock resistance are MON, Motor Octane Number, and RON, Research Octane Number. The MON is the more stringent test, so RON numbers are higher than MON. Thus, when the EPA and gas companies post the 'Pump Octane Number' that is calculated by averaging the two, it results in number than is less than the RON rating.

From memory, 91 RON was the minimum acceptable level for 'Regular' gas established in the '70-'72 EPA regulations for unleaded gas, so 87 pump octane gas equals 91 RON.

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