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One of my coworkers says his chemistry teacher told them (a long time ago) that kerosene has a higher octane value than gasoline. My understanding was always that aviation gasoline has octane value above 120, but it is really gasoline, while kerosene is more like diesel fuel. What is the truth?

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    $\begingroup$ I'm not sure what you are asking. Do you understand what octane means? I think you might be confusing avgas octane with the energy content of a fuel. E.g. diesel has a lower octane than gasoline but a higher energy density. As far as I know, kerosene is only used in jet engines, therefore the octane rating is not relevant. About the only thing answerable in your question is yes, kerosene is more like diesel. You might want to read those articles then reconsider your question. $\endgroup$ – Simon Apr 22 '16 at 7:24
  • $\begingroup$ No, I'm not confusing octane with energy content. If, theoretically, one uses kerosene in an internal combustion engine, will the engine suffer from knocking? $\endgroup$ – Dan Apr 22 '16 at 7:36
  • $\begingroup$ Related: Why do jet engines use kerosene rather than gasoline? and octane rating. $\endgroup$ – mins Apr 22 '16 at 8:07
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Octane rating is a measure of how well a fuel resists detonation, which is the premature explosion of fuel in an engine cylinder before the spark is applied. This is relevant for spark ignition engines which use gasoline type fuels like avgas.

Kerosene has a very low octane rating, somewhere around 15, and isn't a good fuel for spark ignition engines as it would detonate on compression. This is why kerosene and diesel are used in diesel cycle engines which rely on the spontaneous detonation of fuel under pressure. Kerosene is not typically used in internal combustion engines, however in aviation there are turbo-diesel piston engines which run on Jet-A1.

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  • $\begingroup$ Do you have a reference I can show my coworker? $\endgroup$ – Dan Apr 22 '16 at 8:23
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    $\begingroup$ Try googleing "octane rating of kerosene", brings it right up. $\endgroup$ – GdD Apr 22 '16 at 8:27

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