Halderman: Thanks for writing. The octane rating of gasoline goes back to the 1920s when Charles F. Kettering discovered that an engine will operate smoother and quieter if certain additives were used in the fuel. For some background information, I asked Dr. John Heitmann, a professor of history at the University of Dayton, for some input. Here is what he wrote:
“This is actually an incredibly complex and confusing topic. Chemist Russell Marker, while working at Ethyl in 1927, established the octane rating scale of 0-100. What the scale measures is how much compression a fuel can withstand before detonation, with ISO-octane pegged at 100 and N-heptane at 0. That doesn’t mean that a fuel has a proportion of ISO-octane and heptane in it (say 90-10 is 90), but that it behaves in a test as that mixture would. Making matters more confusing, there are Research Octane Numbers (RON) and Motor Octane Numbers (MON) numbers.”
Thanks, Dr. Heitmann, for the background information. Back in the 1960s when high performance muscle cars were popular and performance was king, the research octane method was used and premium was, as you said, 100 octane or higher. Today the octane rating specified and posted on pumps is the average of the two rating methods. For example if a fuel has a research octane rating of 96 and a Motor octane rating of 88, then the posted octane rating would be 92 (R+M/2).
James D. Halderman is an ASE-certified master technician, a member of the Society of Automotive Engineers and the author of 12 textbooks. Submit questions to jim@jameshalderman.com or follow him on Twitter @jameshalderman, or write him in care of: Wheels, Marketing Publications Department, Dayton Daily News, 1611 S. Main St., Dayton OH 45409.
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